The leaders of the Senate foreign relations committee said on Sunday they were on the verge of approving “the mother of all sanctions” against Vladimir Putin, warning there would be no appeasement as the Russian president contemplates an invasion of Ukraine.

“We cannot have a Munich moment again,” the panel’s Democratic chair, Bob Menendez of New Jersey, told CNN’s State of the Union, referring to the 1938 agreement by which allies ceded parts of Czechoslovakia to Hitler, believing it would stave off war.

“Putin will not stop if he believes the west will not respond,” Menendez said. “We saw what he did in 2008 in Georgia, we saw what he did in 2014 in pursuit of Crimea. He will not stop.”

Menendez said he believed bipartisan negotiations for severe sanctions were “on the one-yard line”, despite disagreements with Republicans over whether measures should be imposed before or after any Russian invasion. The UK government promised to ramp up sanctions against Putin and his associates.

Tensions on the Ukraine border continued to escalate with Reuters reporting the Russian military build-up included supplies of blood in anticipation of casualties.

John Kirby, the Pentagon press secretary, told Fox News Sunday: “Putin has a lot of options available to him if he wants to further invade Ukraine, and he can execute some of those options imminently. It could happen really, honestly, at any time.”

Seeking to show bipartisan resolve, Menendez gave CNN a joint interview with his committee’s ranking Republican, James Risch of Wisconsin.

Menendez said: “There is an incredible bipartisan resolve for support of Ukraine, and an incredibly strong bipartisan resolve to have severe consequences for Russia if it invades, and in some cases for what it has already done.

“We are building on the legislation that both Senator Risch wrote independently, and I wrote, which I called the mother of all sanctions. It’s to include a variety of elements, massive sanctions against the most significant Russian banks, crippling to their economy, Russia sovereign debt. These are sanctions beyond any that we have ever levied before.”

Risch said talks had been a “24 hour-a-day effort for the last several days” in an attempt to reach agreement over sanctions timing and content, and that he was optimistic.

“That’s a work in progress,” Risch said, when pressed over discussions about pre-emptive sanctions or measures to be taken in the event of an invasion. “[But] I’m more than cautiously optimistic that when we get back to DC tomorrow that we’re going to be moving forward.”

Menendez said he believed western allies did not have to wait to start penalising Putin.

“There are some sanctions that could take place up front because of what Russia has already done, cyber attacks on Ukraine, false flag operations, the efforts to undermine the Ukrainian government internally,” he said.

“But then the devastating sanctions that ultimately would crush Russia’s economy, and the continuing lethal aid that we are going to send, means Putin has to decide how many body bags of Russian sons are going to return to Russia.

“The sanctions we’re talking about would come later on if he invades, some sanctions would come up front for what has been done already, but the lethal aid will travel no matter what.”

Risch criticized the stance of several far-right figures, including the Fox News host Tucker Carlson and the Kentucky congressman Thomas Massie, who have questioned why the US is backing Ukraine and opposing Russia. Carlson said “it makes sense” that Putin “just wants to keep his western border secure” by opposing moves by Ukraine to join Nato.

“We side always with countries that are democracies, and certainly there isn’t going to be a truce committed in that regard,” Risch said.

“But the people who were saying that we shouldn’t be engaged in this at all are going to be singing a very different tune when they go to fill up their car with gas, if indeed there is an invasion. There are going to be sanctions that are going to be crippling to Russia, it is going to cripple their oil production. And as we all know, Russia is simply a gas station that is thinly disguised masquerading as a country. It is going to have a devastating effect on the economy around the world.”

On NBC’s Meet the Press, Dick Durbin, co-chair of the Senate Ukraine caucus, addressed concerns aired by President Volodymyr Zelenskiy on Friday that growing rhetoric over the crisis was causing panic and destabilising his country’s economy.

His comments followed a call with Joe Biden that Ukraine officials said “did not go well”.

“Any decision about the future of Ukraine will be made by Ukraine,” said Durbin, an Illinois Democrat. “It won’t be made in Moscow or in Washington, in the European Union or in Belarus. It’s their future and their fate and their decision as far as that is concerned.”

The caucus co-chair, Republican Rob Portman of Ohio, who is also on the foreign relations committee, told NBC he believed Putin had underestimated the unity of Nato and others.

“One thing Vladimir Putin has done successfully is he has strengthened the transatlantic alliance and countries around the world who are looking at this and saying, ‘We cannot let this stand, we cannot let this happen’,” Portman said.

“For the first time in nearly 80 years we could have a major and very bloody conflict in Europe unless we stand up together and push back, and so far so good.”