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

Sen. Jeff FlakeJeffrey (Jeff) Lane FlakeFlake donates to Democratic sheriff being challenged by Arpaio in Arizona The Hill's Morning Report - Trump says US-China trade talks to resume, hails potential trade with Japan, UK Joe Arpaio to run for Maricopa County sheriff in 2020  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 PortmanThe Hill's Morning Report - Trump takes 2020 roadshow to New Mexico The 13 Republicans needed to pass gun-control legislation Hillicon Valley: Google to promote original reporting | Senators demand answers from Amazon on worker treatment | Lawmakers weigh response to ransomware attacks 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.