President Donald Trump‘s “trust” in Russia’s Vladimir Putin now faces a major test as the world waits for Moscow to respond to a 30-day ceasefire proposed by the U.S. and accepted by Ukraine.

Trump said after Tuesday’s breakthrough in Saudi Arabia that he would speak with Putin soon, though declined to comment on Wednesday when asked if anything had been scheduled.

“I’ve gotten some positive messages, but a positive message means nothing,” he said from the Oval Office, where he was peppered with question on what comes next. “This is a very serious situation.”

The Kremlin has cautiously said it is reviewing the proposal and it will not be pushed into anything.

The Trump administration placed significant pressure on Ukraine in recent weeks in stopping military aid and pausing some intelligence sharing — both resumed only after Ukraine agreed to the ceasefire on Tuesday.

U.S. officials, including Trump himself, have also set limited expectations amid broader negotiations on Ukraine’s borders and expressly ruled out NATO membership for the Eastern European ally.

Meanwhile, they’ve not publicly demanded any concessions from Putin — and it’s not clear how far Trump is willing to go in pressuring Russia to accept the 30-day ceasefire.

“We can, but I hope it’s not going to be necessary,” Trump said on Wednesday when asked about that very issue.

“There are things you could do that wouldn’t be pleasant in a financial sense,” he added without divulging any specifics. “I can do things financially that would be very bad for Russia. I don’t want to do that because I want to get peace.”

Trump last Friday threatened sanctions on Russia until it reached an agreement with Ukraine. The Biden administration imposed hundreds of sanctions on Moscow over the course of the conflict.

Secretary of State Marco Rubio earlier on Wednesday noted that Russia is already “pretty sanctioned up” as he was asked what pressure the administration would be ready to apply.

“As far as I am aware, the United States has not provided armaments to Russia,” Rubio said as he largely sidestepped the inquiry. “The United States is not providing assistance to Russia. Every single sanction that has been imposed on Russia remains in place … So my point being is that there’s been no steps taken to relieve any of these things, these things continue to be in place.”

“We don’t think it’s constructive for me to stand here today and begin to issue threats about what we’re going to do if Russia says no, let’s hope they say yes,” Rubio said.

Trump has also often praised his relationship with Putin, saying he knows him “very well” and declining to call him a dictator despite using the term to describe Ukrainian President Volodymyr Zelenskyy.

“I think he wants peace. I think he would tell me if he didn’t,” Trump said of the Russian leader in mid-February. “I trust him on this subject. I think he’d like to see something happen.”

Just last week, in an interview with Fox News, Trump claimed Putin was “more generous” and easier to work with than Ukraine.

Now, the administration is saying the ball is in Russia’s court after Ukraine agreed to an immediate, monthlong stoppage in hostilities should Moscow do the same.

“We’ll see what their response is,” Rubio said. “If their response is yes, then we know we’ve made real progress and there’s a real chance of peace. If their response is no, it will be highly unfortunate and then it’ll make their intentions clear.”

ABC News’ Patrick Reevell and Kelsey Walsh contributed to this report.