There are only two possible outcomes following President Donald Trump’s historic summit with North Korean leader Kim Jong-un on Tuesday — peace or war — Sen. Lindsey Graham (R-S.C.) said Sunday on ABC News’ “This Week.”

“There’s three outcomes here: peace, where we have a win-win solution; military force, where we devastate the North Korean regime and stop their program by force; or to capitulate, like we’ve done in the past, and Donald Trump is not going to capitulate. So there’s really only two options: peace or war,” Graham said.

Trump will become the first U.S. president to meet with North Korea’s leader since the communist nation was formed in 1948. Both Trump and Kim arrived in Singapore over the weekend to prepare for their meeting to discuss denuclearization and the future of Kim’s regime.

“I don’t expect a deal next Tuesday. I expect the process to be started next Tuesday,” Graham added. “We’ll know diplomatic failure when we see it … We’ll find out in about a year if [talking with North Korea] is going to work.”

The senator urged his Democratic colleagues to “back the president up” instead of resisting him or thwarting his diplomatic efforts.

Senate Democrats penned a letter to Trump last week outlining a set of demands for any North Korea deal that may arise from the summit.

“Sanctions relief by the U.S. and our allies should be dependent on dismantlement and removal of North Korea’s nuclear weapons and ballistic missile programs,” Senate Minority Leader Chuck Schumer (D-N.Y.) and Sen. Bob Menendez (D-N.J.) wrote in their letter.

“We believe that Congress therefore has an important role to play in working with the administration to support your efforts and to shape U.S. policy toward North Korea,” Schumer and Menendez said. “However, we also believe that Congress must act as a check on any agreement that does not live up to these principles by imposing tougher sanctions and oversight.”

Schumer added during a press conference, “If we think the president is veering off course, we won’t hesitate to move, but let’s see where he’s headed.” And in an interview with NPR, the Democratic leader said, “The worry we have is the president will be so eager for, quote, ‘an agreement’ that it won’t protect the security, first and foremost, of the United States.”

But Graham rebuked his Democratic colleagues and urged them to support Trump’s diplomatic efforts and respect the office of the presidency.

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“I appreciate you telling the president what a good deal would look like, but the country needs you to back the president up to get a deal,” he said. “So here’s the question for my Democratic colleagues … If diplomacy fails, will you support my efforts to authorize use of military force as a last resort to convince North Korea and China things are going to be different this time?”

Graham insisted that bipartisan military-force authorization would make the Senate Democrats’ letter “much more credible. And if diplomacy fails, as a last resort, Democrats and Republicans need to put the military option on the table or we’ll never get a good deal.”

The senator also chided his Democratic colleagues, saying, “I wish they had sent such a letter to President [Barack] Obama regarding the Iranian nuclear efforts.”

The GOP senator emphasized during an interview on Fox News’ “Sunday Morning Futures with Maria Bartiromo” that using the military operation would be the “last resort.”

“North Korea’s not going to change the way they do business unless they believe that the military option’s on the table,” Graham insisted.

PoliZette writer Kathryn Blackhurst can be reached at [email protected]. Follow her on Twitter.