A bipartisan group of senators is within striking distance of a deal on a bill that would impose crippling sanctions on Russia for its hostilities against Ukraine.
"We are finding the path forward very clearly," said Sen. Jim Risch, top Republican on the Foreign Relations Committee, indicating that the White House and other key agencies were involved in the negotiations to agree on a deal ahead of any potential invasion by Russia, which has amassed more than 100,000 troops on Ukraine's border.
Asked if a deal could be announced as early as Thursday, Risch said, "I'd have to say that's possible," though aides to three senators involved said it was unlikely.
Top Biden administration officials briefed members of Congress on Thursday about the escalating tensions in and around the former Soviet Republic. Lawmakers leaving the more than hourlong briefing in the Congressional Visitor Center said the gravity of the message from those top officials, including Secretary of Defense Lloyd Austin, Chairman of the Joint Chiefs of Staff Gen. Mark Milley, Secretary of State Antony Blinken and CIA Director Avril Haines, added urgency to their efforts.
"Collectively, what I heard made the case that this is more pressing, more timely, and that time in this regard, if we want to be preventative, is of the essence," said Committee Chairman Bob Menendez, D-N.J. Menendez, who is the chief architect of the sanctions bill along with Risch, added that he is "cautiously optimistic that we are going to get there."
Sen. Lindsey Graham, R-S.C., who is involved in the bipartisan Senate talks, agreed, saying, "The briefing, I think, will accelerate the bipartisan sanctions package."
Despite the closeness of a deal, differences remained among negotiators on the appropriate triggers for sanctions and when and how to penalize those developing the controversial, but as-yet-inoperable Russia-to-Germany Nord Stream 2 pipeline, a project that would bypass Ukraine, taking with it crucial revenue.
"I am hopeful in the next coming days we can introduce a sanctions package that imposes sanctions now for the (Russian) provocation with post-invasion sanctions that will destroy the Russian economy as we know it," said Graham, who like many Republicans after the briefing, said he thought a Russian invasion of Ukraine was now a matter of "when" not "if."
Some Democrats and the Biden administration want to hold back sanctions, arguing that they are more powerful as a deterrent against Russian aggression.
"Deterrence is the idea that if you do X, we will do Y. If you put penalties in place in advance, at least significant penalties, you obviously take away the stick of deterrence," said Sen. Chris Van Hollen, D-Md., a member of the Foreign Relations Committee.
"I think it's very important that (the) United States put a very strong sanctions package in place," Sen. Tim Kaine, D-Va., told CNN, adding that any sanctions need to be announced in advance "to have a deterrent effect."
House Speaker Nancy Pelosi said sanctions against Russia must be "much more forceful than they have been" but also insisted that any sanctions be imposed after an invasion.
"I think it's really important for us to use the sanctions if the Russians strike," Pelosi, D-Calif., told reporters Thursday. "It is important because it's where leverage is at maximum. If they do this, then we strike."
Pelosi said that thinking is also in line with most U.S. allies.
"This is deadly serious," Pelosi said. "So, they have to feel the pain, and it has to be felt right up to the richest man in the world: Vladimir Putin. Nobody knows what he's going to do except for him."
Indeed, lawmakers have said the legislation, a bill Menendez said puts in place "the mother of all sanctions," would contain a strong recommendation that Russia be kicked out of the global financial consortium known as SWIFT, or the Society for Worldwide Interbank Financial Telecommunications. Based in Belgium, it connects more than 11,000 financial institutions and is used as a messaging platform for the transfer of funds around the world.
If that recommendation is included in the bill, the Biden administration would still have to take action to have Russia removed, an extreme action lawmakers have said is on the table.
The White House confirmed Thursday that it is in close consultation with senators but stopped short of endorsing any deal.
"We are in very close touch with members of Congress about this legislation, which I don't think has been formally even proposed yet," White House press secretary Jen Psaki told reporters en route to New York aboard Air Force One. "So we are in close contact and in conversations with them."
Psaki, however, continued to express the administration's support for post-invasion sanctions, saying that the "deterrent" approach of "the crippling economic sanctions package" and noting that the impact is already being felt in the Russian financial markets.
Still, a number of Democrats were moving closer to the GOP position that pre-invasion sanctions were a must even if the most serious sanctions are reserved in the event of an invasion.
"I think Putin and Putin's Russia have already committed sufficient aggression against Ukraine justifying some sanctions," said top Biden ally Chris Coons, D-Del. "I think we should hold back the most aggressive and most punishing sanctions for now as a deterrent because the whole goal here is to keep open some space for diplomacy and to deter aggression."
Menendez and Risch have been briefing members of their panel this week. One member -- Mitt Romney, R-Utah -- told ABC News he met with Risch on Wednesday night and the smaller group negotiating the package is "making good progress."
The legislation would include a measure authored by Sens. John Cornyn, R-Texas, and Ben Cardin, D-Md., modeled on the World War II-era "lend-lease" program, which would use existing presidential authorities to allow the administration to provide lethal military equipment to Ukraine to protect the population from a Russian invasion.
Members hope to move any sanctions deal -- which, according to two aides involved in the matter, is still in the legislative drafting stage -- to the Senate floor quickly, and Sen Chris Murphy, D-Conn., who recently returned from Ukraine and is part of the talks, told ABC News he had spoken earlier in the week with Senate Majority Leader Chuck Schumer, who committed to bringing any bipartisan deal to the floor for a vote quickly.
And after Thursday's high-level briefing, it is clear that members are ready to act swiftly.
Coons said he's "very" concerned about the situation on the ground in and around Ukraine, adding, "It's really hard to listen to all of that and not conclude that we need to do more."
ABC News' Mariam Khan and Ben Gittleson contributed to this report