WASHINGTON — Secretary of State Mike Pompeo’s planned testimony on Capitol Hill Wednesday will test his ability to explain President Trump’s apparent affinity toward Russia — and the will of Republicans who control Congress to get to the bottom of it.

Pompeo’s appearance before the Senate Foreign Relations Committee comes amid a series of high-profile Trump foreign policy ventures.

The president drew widespread criticism at a meeting with Russian President Vladimir Putin in Helsinki earlier this month where he appeared to side with Putin over U.S. intelligence agencies over evidence of Russian meddling in the 2016 election.

That meeting followed Trump’s summit with North Korean Leader Kim Jong Un in Singapore in June, where the two signed a document agreeing to the eventual denuclearization of the Korean peninsula with no specifics on how to do so.

Trump also fired off a bellicose tweet at Iran this week, warning of severe “consequences” for perceived threats against the U.S.

Pompeo spoke favorably about the Helsinki summit on Tuesday, ahead of his Senate testimony.

"There are many things that came from what I view as an incredibly important meeting between President Trump and President Putin, one that i think the world will have benefited from when history is written,” Pompeo said at a press conference in California.

In interviews with members of the committee on Tuesday off the Senate floor, lawmakers said the hearing will revolve around two questions to Pompeo: “What happened in Helsinki? What happened in Singapore?” — both places where Trump cut still-undefined deals in private with two of the world’s most dangerous leaders.

Sen. Bob Corker, R-Tenn., who chairs the committee, scheduled the hearing shortly after Trump returned from Helsinki and made clear he expected Pompeo to attend.

“Hopefully he can clarify what actually happened, if anything, in North Korea, what commitments were made in Russia … and talk to us a little about NATO,” Corker said.

Secretary of State Mike Pompeo before boarding his plane at Sunan International Airport in Pyongyang, North Korea, on July 7. Andrew Harnik / Pool via AP file

Pompeo had previously scheduled, then cancelled, a classified briefing for all senators following the Singapore summit.

“I thought we were going to have one with him and (Defense Secretary) Mattis a month ago. It was cancelled at the last minute,” Corker said.

Both Democrats and Republicans issued statements last week in support of U.S. intelligence agencies after Trump — standing alongside Putin in Helsinki — called past U.S. actions “foolish” and cast doubt on the agencies’ assessment that Russia attacked U.S. elections in 2016. Trump partly walked back his comments amid the outpouring of criticism he received, but still invited Putin for a meeting in Washington this fall.

Lawmakers told NBC News they would press Pompeo on what took place in Trump’s two-hour private conversation with Putin.

“First and foremost, what commitments were made during that meeting?” said Sen. Jeff Flake, R-Ariz., a frequent Trump critic.

“Did it have to do with troop placements, military exercises in Europe, NATO expansion, Russia and Syria? We have no idea what was said,” Flake added.

“There’s a lot of concern” about a proposed second meeting with Putin, Flake said, especially if Trump insists that it, too, should be a one-on-one conversation.

“We ought to push back heavily there,” Flake said.

Some Republicans want to show they’re willing to provide a check on Trump’s foreign policy, in particular when it comes to Russia.

In the Senate, two separate bills proposing tighter sanctions on Russia have Republican co-sponsors, including Sens. Marco Rubio of Florida and Lindsey Graham of South Carolina, Corker on Tuesday announced a series of meetings on Russia, a day ahead of Pompeo’s testimony.

Sen. Rob Portman, R-Ohio, said the sanctions bills would likely be brought up in the hearing.

“The question is: Do you wait for additional Russian meddling to have the sanctions go into effect or do you put them into effect now knowing that they did meddle in our election in 2016 and there is evidence they are preparing to do the same (in 2018)?” he said.

Many Democrats are skeptical Republicans will really follow through with legislation. Senate Minority Leader Chuck Schumer said his GOP colleagues are “stuck in the mud” when it comes to punitive actions against Russia.

Indeed, while Senate Majority Leader Mitch McConnell said Tuesday that Putin "will not be welcome up here, at the Capitol" if he comes to Washington, he would not commit to allowing a vote on some form of sanctions legislation. “I think there’ll be some hearings on that,” he told NBC.

“My expectations are low” regarding Pompeo’s testimony before the committee, Sen. Chris Murphy, D-Conn., said. “Pompeo’s in a tough spot. He doesn’t know what the foreign policy of this country is. The president bobs and weaves on a daily basis.”

Sen. Jeanne Shaheen, D-N.H., likewise said she didn’t expect to get much vital information from Pompeo in the one round of questioning allowed for each senator.

For his part, Portman said Wednesday’s hearing had the potential to be revelatory.

“You’ve seen him in testimony before, he sometimes is very informative. So it could be an interesting hearing,” Portman said with a chuckle. “He’s not shy about saying what his point of view is.”

When asked if you expect him to contradict the president on some issues, Portman added: “Perhaps. Stay tuned.”