WATCH: Sen. Flake: “More doubtful” North Korean summit will happen 

Sen. Jeff FlakeJeffrey (Jeff) Lane FlakeFlake urges Republicans to condemn 'vile and offensive' Trump tweets Flake responds to Trump, Jimmy Carter barbs: 'We need to stop trying to disqualify each other' Jeff Flake responds to Trump's 'greener pastures' dig on former GOP lawmakers MORE (R-Ariz.), a frequent critic of President Trump, says he’s “more doubtful” that the planned meeting between the president and North Korean leader Kim Jong Un, slated for June 12 in Singapore, will happen.

“I don’t know — it looks more doubtful to me,” Flake told The Hill when asked if he thinks the summit will happen, adding, "But you know, I'm glad that we are talking. I’ve never put much hope in that meeting.”

Flake's comments come as North Korea warned earlier this week that it could pull out of the summit due to military exercises by the U.S. and South Korea.

Flake added that he thinks it takes more than one month of “prep work” for a meeting of “that significance.” 

Fellow GOP Sen. Rob PortmanRobert (Rob) Jones PortmanFighting the opioid epidemic: Congress can't just pass laws, but must also push to enforce them The Hill's Morning Report - Presented by JUUL Labs - House to vote to condemn Trump tweet Rising number of GOP lawmakers criticize Trump remarks about minority Dems MORE (Ohio) was more optimistic that the Korean summit will go forward despite North Korea’s threats.

“Do I trust them? No,” Portman said, “Do I want to talk with them directly government to government? Yes. And I think we can move forward on that.”

House Armed Services Committee member Rep. Steve Russell (R-Okla.) told The Hill he also predicted “the meeting will still occur,” even if Kim sounds off ahead of time. 

“I guess he doesn’t want to look like a doormat — he’s trying to sound tough or whatever it might be prior to the negotiations — OK, we can live with rhetoric, we can live with that,” Russell said.

Click on the video above to hear the lawmakers in their own words.