Republican presidential candidate John Kasich held a press conference in New York on Thursday in which he argued rival Donald Trump isn't "prepared" to be president in a convenient.
"I had to list five things that continue to prove that Donald Trump is clearly not prepared to be president of the United States, commander-in-chief, leader of the free world," Kasich said, speaking at a hotel off Times Square.
John Kasich: Here are 5 ways Donald Trump proved he shouldn't be president in the past 24 hours
MT. PLEASANT, SC - FEBRUARY 10: Republican presidential candidate John Kasich talks to an overflow crowd outside of Finn's Brick Oven Pizza February 10, 2016 in Mt. Pleasant, South Carolina. The South Carolina Republican primary will be held Saturday, February 20. (Photo by Sean Rayford/Getty Images)
11/3/95 - Rep. John R. Kasich (R-OH), seated 2nd from left, and Sen. Pete V. Domenici (R-NM) in the dark suit standing, go over their response to President Clinton's radio address just prior to recording the radio broadcast in the Senate studio. Kasich was casually dressed as the House was out of session for the weekend. (Photo by Robert A. Reeder/The Washington Post/Getty Images)
House Budget Committee Chairman Rep. John Kasich, R-Ohio, holds the Republican budget plan during a debate with Budget Director Alice Rivlin, Thursday Oct. 19, 1995 at the National Press Club in Washington. Kasich said that the Republicans have a deal to balance the budget in seven years and will not wait to balance any longer. (AP Photo/Doug Mills)
House Budget Committee Chairman Rep. John Kasich, R-Ohio, points to his head during a Capitol Hill news conference Thursday Nov. 16, 1995 to discuss the federal budget impasse. Earlier, President Clinton pledged to veto the latest Republican attempt to end the three-day-old partial federal shutdown, dismissing the GOP measure as "an exercise of political power." (AP Photo/Doug Mills)
U.S. Rep. John Kasich, R-Ohio, flashes the victory sign as he walks with his new bride, Karen Waldbillig, down the steps of St. John's Episcopal Church in Worthington, Ohio, after the couple exchanged wedding vows Saturday, March 22, 1997. Kasich and Waldbillig, who had been dating for eight years, plan to build a home in Delaware County. (AP Photo/Elizabeth Ellis)
D:\BOB\budget3.tif - slug: NA/BUDGET date: May 2, 1997 photog: Robert A. Reeder TWP The Rotunda of the Capitol description: GOP happy with their signed budget John R. Kasich (R-OH) is having a particularly good time during the GOP announcement of a new budget in the Rotunda of the Capitol. In front of him is Speaker Newt Gingrich. (Photo by Robert A. Reeder/The Washington Post/Getty Images)
Rep. John Kasich, R-Ohio, left, shakes hands with Sen. Pete Domenici, R-N.M., during the announcement of the budget Friday, May 2, 1997, at the Capitol. Trading combat for compromise, President Clinton and Republican congressional leaders announced agreement Friday on a plan to balance the budget while bestowing tax breaks on families, investors and students. (AP Photo/Joe Marquette)
As his wife Karen, left, watches, U.S. Rep. John Kasich, R-Ohio, stops in for a haircut by Joe Swiezynski in Milford, N.H. Monday Feb. 15, 1999. Kashich is on a two-day campaign swing through New Hampshire seeking support for his presidential bid in the nation's earliest presidential priamry scheduled for about a year from now. (AP Photo/Jim Cole)
Presidential hopeful Sen. John Kasich, R-Ohio, center, rides a dog sled Sunday, March 14, 1999, on Lake Winnepesaukee in Laconia, N.H. Kasich participated in the World Championship Sled Dog Derby award ceremony and is in the state looking for support for his run for president in 2000. (AP Photo/Joel Page)
John Kasich, Republican Congressman from Ohio and presidential hopeful, makes a point during an interview on a stop on a campaign swing through Los Angeles on Tuesday, March 30, 1999. (AP Photo/Reed Saxon)
Rep. John Kasich, R-Ohio, warms up before a celebrity softball game Saturday, July 3, 1999, in Dyersville, Iowa. Kasich and fellow presidential hopeful Bill Bradley were part of a unique mix of baseball and politics, as presidential candidates and Hall of Fame legends took up the cause of a disgraced player who died nearly 50 years ago. Nostalgia and baseballs filled the air in a city put on the map by the movie ``Field of Dreams,'' which was about a fantasy baseball game involving Shoeless Joe Jackson. (AP Photo/Rodney White)
P 350430 022 2May99 Manchester, Nh John Kasich (R-Oh), At The First-In-The-Nation Primary Kick-Off Weekend. (Photo By Jonathan Elderfield/Getty Images)
Republican presidential hopeful, Texas Gov. George W. Bush, left, and Rep. John Kasich, R-Ohio, sport Bush baseball caps during a news conference in Washington Wednesday July 14, 1999 where Kasich announced he would end his campaign for the Republican presidential nomination and endorse Bush. (AP Photo/Doug Mills)
ADVANCE FOR SUNDAY NOV. 5--With the Washington Monument in the background, retiring Rep. John Kasich, R-Ohio poses on Capitol Hill Thursday, Oct. 19, 2000. (AP Photo/Stephen J. Boitano)
UNITED STATES - FEBRUARY 02: HOUSE ARMED SERVICES--John R. Kasich, R-Ohio, and Duncan Hunter, R-Calif., talk during House Armed Services Committee hearing on the president's fiscal year 2000 defence budget authorization budget request. (Photo by Douglas Graham/Congressional Quarterly/Getty Images)
Former Ohio congressman John Kasich attends the Republican National Convention at the Xcel Energy Center in St. Paul, Minnesota, Wednesday, September 3, 2008. (Photo by Harry E. Walker/MCT/MCT via Getty Images)
WASHINGTON, DC- Dec. 01: Governor-elect John Kasich, R-Ohio, and House Minority Leader John A. Boehner, R-Ohio, during a news conference after their meeting with other Republican members and governors-elect. Boehner is the presumed House Speaker for the 112th Congress. (Photo by Scott J. Ferrell/Congressional Quarterly/Getty Images)
John Kasich, governor of Ohio, speaks during a groundbreaking ceremony for the Cleveland Medical Mart and Convention Center in Cleveland, Ohio, U.S., on Friday, Jan. 14, 2011. The Cleveland Medical Mart and Convention Center will include a 100,000 square foot medical mart and an adjoining convention center with 230,000 square feet of exhibit hall space. The facility is expected to open in September 2013. Photographer: David Maxwell/Bloomberg via Getty Images
COLUMBUS, OH - MARCH 30: Ohio Governor John Kasich works long hours with staff on his new budget proposal at his office, in the Ohio State House office, Columbus, Ohio, Wednesday, March 30, 2011. Newly elected republican Ohio Governor John Kasich is working toward to balancing an Ohio budget in deficit through a budget proposal with extensive budget cuts, spending reform, and changes in labor laws, including restrictions on collective bargaining. (Photo by Melina Mara/ The Washington Post via Getty Images)
US Republican presidential candidate and former Massachusetts Governor Mitt Romney (2nd L) waves alongside Ohio Republican Senator Rob Portman (L) and Ohio Governor John Kasich (R) during a campaign stop at Tom's Ice Cream Bowl in Zanesville, Ohio, on August 14, 2012. AFP PHOTO / Saul LOEB (Photo credit should read SAUL LOEB/AFP/GettyImages)
UNITED STATES - AUGUST 28: Ohio Gov. John Kasich speaks at the 2012 Republican National Convention at the Tampa Bay Times Forum. (Photo By Chris Maddaloni/CQ Roll Call)
COLUMBUS, OHIO - JULY 21: Ohio Governor John Kasich gives his speech announcing his 2016 Presidential candidacy at the Ohio Student Union, at The Ohio State University on July 21, 2015 in Columbus, Ohio. Kasich became the 16th candidate to officially enter the race for the Republican presidential nomination. (Photo by Ty Wright/Getty Images)
CONCORD, NH - FEBRUARY 09: Republican presidential candidate Ohio Governor John Kasich waves to the crowd after speaking at a campaign gathering with supporters upon placing second place in the New Hampshire republican primary on February 9, 2016 in Concord, New Hampshire. Kasich lost the Republican primary to Donald Trump, though he upset fellow Republican governors Chris Christie and former Governor Jeb Bush. (Photo by Andrew Burton/Getty Images)
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Trump also said he wouldn't take the option of using nuclear weapons in Europe off the table. Kasich said he found that unacceptable.
During his press conference, Kasich was pressed on whether his vow to support the eventual Republican nominee still held true. Kasich insisted he did not believe that Trump, the clear GOP frontrunner, would become the nominee. But despite his opposition to Trump, he did not rule out ultimately endorsing him.
"This will go to the convention," he replied. "Let's see who they pick at the convention. At that point, I'll make a decision about my endorsement."
Here are the five reasons Kasich listed why Trump cannot be president:
1: His abortion comments
Kasich said Trump's abortions comments are "putting women in a very difficult position." He also said presidents don't get do overs.
2: His refusal to rule out using nuclear weapons
"He actually talked about the use of nuclear weapons, both in the Middle East and in Europe," Kasich said. "You wonder about his hand or his thumb getting any closer to the critical button that presidents are in charge of."
3: His stance on torture
"He says that we should basically abolish the Geneva Convention, which was created to make sure we had fair treatment for anybody who was captured in war," Kasich continued. "And somehow we ought to abolish the Geneva Convention and engage in I guess more torture."
4: His stance on NATO
"He's called on NATO to basically be abolished," Kasich said. "Although I can't figure out what his position is today," he added.
5: His expectations from a potential Supreme Court justice
"I don't even know how he went there," Kasich said.
"Donald Trump suggested that any Supreme Court justice must make a commitment to investigate and review Hillary's emails. That, I don't even know how you do that. That's something I can't even figure out."