Heavyweight US Republican senators and former Democratic presidential nominee Hillery Clinton expressed concern Tuesday after President Donald Trump said he would be "honored" to meet with North Korean leader Kim Jong-un.

Trump made the remark in an interview with Bloomberg News on Monday, arguing that he would "absolutely" be willing to meet with Kim if such a meeting takes place "under the right circumstances."

The use of the word "honored" toward the autocratic leader raised eyebrows.

"I don't understand it and I don't think that the president appreciates the fact that when he says things like that it helps the credibility and the prestige of this really outrageous strongman," McCain, chairman of the Senate Armed Services Committee, said on MSNBC.  "The largest gulag left on earth is in North Korea. And we all know about their human rights abuses and others."

Sen. Lindsey Graham (R-SC) also said such a meeting could "empower" the North's dictator.

"I'd find it very hard for me to sit down across the table from a guy who makes Bashar Assad look like a choir boy," Graham said on CNN. "If you understand what he (Kim) does to his own people, you'd be repugnant to be in the room with him."

Graham also told reporters later that he would caution about such a meeting "because you empower anybody you meet."

"But if (President Trump) can find a way to stop North Korea from developing an ICBM with a nuclear weapon on top of it to hit America and that includes meeting him, count me in," he said.

Clinton said the US should be careful about negotiations with the North.

"The North Koreans are always interested, not just Kim Jong-un but his father before him, were always interested in trying to get Americans to come to negotiate to elevate their status and their position. And we should be very careful about giving that away,"

Clinton said at a Women for Women International event.

"Negotiations are critical, but they have to be part of a broader strategy, not just thrown up on a tweet some morning that, 'Hey let's get together and, you know, see if we can get along and maybe we can come up with some sort of a deal.' That doesn't work," she said.

The "honored" remark came after Trump made a series of positive comments on the North's leader.

In media interviews last week, Trump praised Kim, and even called him a "pretty smart cookie," for taking over power from his father at a young age while dealing with "very tough people" trying to take power away from him, including his uncle, whom Kim executed.

McCain said that US Republicans have always stood up for human rights and against dictatorships.

"This is a dramatic departure from the kind of approach to foreign policy and human rights that I admired Ronald Reagan so much for. And I think one of the reasons why he was one of the most successful presidents in history," he said. "it's very disturbing.

It's disturbing because we are proud Republicans and we stand for human rights."

Trump also came under fire for his "very friendly" phone call Saturday with Philippine President Rodrigo Duterte.

"I wish that the president would consider much more carefully his comments, particularly in praise of a North Korean. He's worse than a dictator. He's a despot. He's a -- I've run out of adjectives and adverbs," McCain said.

"And this guy in the Philippines has praised extrajudicial killings of people, 7,000 I've read have been killed. You can't praise that kind of behavior and not raise concerns around the world," he said.

Rep. Ed Royce (R-CA), chairman of the House Foreign Affairs Committee, said that the "right circumstances" for Trump's talks with the North's leader should be for the regime to "stop its atomic weapons program and for North Korea to change its policies in terms of its treatment of its people."

"If Kim Jong-un changes his policies and allows political prisoners to be released and stopped his nuclear weapons program, I think we’re in concurrence that we would be able to have these discussions," Royce told reporters after receiving a medal from South Korea's government for his contributions to the Korea-US alliance.

"Obviously, now is not the time. Now is not the time for those discussions because right now is the time to work with Beijing and the rest of the international community in order to put pressure on North Korea to stop its nuclear weapons program," he said. (Yonhap)