Washington (CNN) For Republicans eager to dismantle Obamacare, President Donald Trump's prime-time address to Congress Tuesday night is shaping up as a high-stakes proposition.

More than five weeks after Inauguration Day, Trump is set to deliver a speech that lays out his vision for the country and highlights his most urgent policy priorities. Trump has said that repealing and replacing the Affordable Care Act is at the top of his agenda --- but so far, his public remarks about overhauling the health care system have proved to be a mixed bag for fellow Republicans.

On Monday, on the eve of his joint address to Congress, Trump was characteristically blunt. "Now, I have to tell you, it's an unbelievably complex subject," Trump said about health care reform during a meeting with governors. "Nobody knew health care could be so complicated."

The comments acknowledged the myriad of problems GOP leaders have confronted in their efforts to repeal and replace Obamacare.

"It's complicated. In fact, it's almost impossible, but we'll figure it out," said GOP Senate Finance Committee Chairman Orrin Hatch.

House Speaker Paul Ryan and Senate Majority Leader Mitch McConnell want to see Trump offer more specifics on health care -- and publicly back the House GOP plan, sources tell CNN.

During a meeting at the White House on Monday, Ryan was given the impression that the administration is embracing much of the House GOP plan on Obamacare and that the President will make that clear in his speech.

This should help reassure House Republican leaders and their aides, some of whom had been growing increasingly concerned by the President's unwillingness to embrace -- or, many believe, fully understand -- the congressional approach to health care.

If Trump doesn't better articulate his support for their plan, "it is in trouble," a GOP Hill aide said earlier in the week.

"This is a critical moment for him to get behind this," another senior Republican congressional aide said.

Top Republicans have been slowed down by numerous intra-party disagreements , including over how much of the health care law to repeal and how fast.

Rep. Mark Meadows , the chairman of the conservative House Freedom Caucus Chairman, told CNN Monday that he would not support a draft of the House GOP leadership's repeal bill that was leaked last week. Rep. Mark Walker, chairman of the Republican Study Committee, announced his opposition hours later. A widespread defection within the conservative wing of the party could tank the party's efforts to repeal Obamacare altogether.

Republicans are hoping that Trump will seize Tuesday night's closely watched speech to send a unifying message on Obamacare.

"We talk about (health care) all day every day so we've got lots and lots of ideas. They need to be brought together in a single course and agreed on. That's where we need to be," Idaho Republican Sen. Jim Risch told CNN. "He's the president. He needs to be part of this also."

The leaked House bill revealed Republicans are eying major cuts to Obamacare's Medicaid expansion -- a tension point for some Republican governors who have benefitted from the boost in federal dollars. The plan also included a defunding of Planned Parenthood, something that moderate Republicans like Alaska Sen. Lisa Murkowski have already drawn a line against supporting.

Giving urgency to repealing Obamacare

Some Republicans are also banking on Trump to inject a much-needed sense of urgency into the Obamacare debate.

"I'm hopeful that in his address, he encourages to take action much quicker. I would never have guessed that we'd be near the first week of March without passing a substantial piece of legislation as it relates to the repeal of the Affordable Care Act," Meadows told CNN.

"Time is not our friend," he added. "If it doesn't get accomplished in the first 200 days, it probably doesn't get accomplished."

Behind the scenes, Trump is pushing Congress to move faster.

According to Democratic Virginia Gov. Terry McAuliffe, Trump told Secretary of Health and Human Services Tom Price in a White House meeting with governors Monday that he wanted to see something sooner than later.

"The President today in our meeting at the White House asked Dr. Price that question (on timing) and he said he'd have something out in three or four weeks, and I think the President said 'I want to see it in two' or something," McAuliffe said. "I know the White House is pushing coming up with something."

Insurance for everybody?

There's no denying that Trump -- at times -- has also been a hindrance to Republicans in Congress.

On multiple occasions, Trump has frustrated and confused Republicans on the Hill with unexpected -- and sometimes even seemingly off-the-cuff -- public comments about both the status and goal of rolling back Obamacare.

Days before being sworn in, Trump raised eyebrows when he declared that he was putting the finishing touches on an Obamacare replacement plan that aims to provide "insurance for everybody.

The comments were problematic for more reasons than one: even senior GOP lawmakers had no idea what plan the President was referring to, while the promise of "insurance for everybody" deviated from the usual Republican talking point that emphasizes access to coverage rather than universal coverage.

Trump also sent lawmakers scrambling and wondering whether to take his words literally when he demanded that the GOP take a vote to repeal and replace Obamacare on an impossible timeline.

Few are counting on Trump's speech to settle years' worth of Republican disagreements on health care, however.

"I would expect that this will be a speech that doesn't have a lot of specifics, but continues to emphasize the President's agenda," said Missouri Republican Sen. Roy Blunt.

Trump told governors Monday that his speech is going to focus heavily on security and less on the specifics of health care.

"The President said today that his speech is going to be focused on defense, so I obviously take him at his word," Republican Nevada Gov. Brian Sandoval said. "What he did tell us today is Secretary Price is going to be coming up with some type of plan in the next few weeks."