A group of congressional Democrats including the former House speaker Nancy Pelosi and armed services veterans urged the current Republican speaker, Mike Johnson, to “lead, follow or get out of the way” of more military support for Ukraine in its war against Russian invaders.

“In the military, we have a great expression,” Mikie Sherrill, a House Democrat from New Jersey and a former navy helicopter pilot, told reporters on Capitol Hill. “‘Lead, follow or get out of the way.’ That is exactly what our speaker has to do.”

Last month, Senate Democrats and Republicans passed a $95bn foreign aid package covering Ukraine, Taiwan and Israel.

The Democrats who spoke on Wednesday faced vocal competition from protesters with Code Pink: Women for Peace opposing funding for Israel in its war against Hamas. On Ukraine policy, though, House Republicans have proved more obstructive than Medea Benjamin, the Code Pink co-founder, was able to be at the Capitol.

Under the direction of Donald Trump, the presumptive presidential nominee who openly favors Russia and its president, Vladimir Putin, Johnson has shown no sign of bringing the Senate package up for a vote. The Hungarian prime minister, Viktor Orbán, recently emerged from meeting Trump to say that if Trump is re-elected, he will not give “a penny” to Ukraine.

Trump has said he will encourage Russia to attack US allies he deems not to pay enough to be members of Nato.

House Democrats have lodged discharge petitions, a mechanism by which the speaker can be bypassed. Despite significant Republican support for Ukraine aid such efforts remain unlikely to succeed. On Wednesday, one petition was about 50 votes short of success.

Johnson, Sherrill said, “has to show some leadership and put this bill on the floor so we can get an up-or-down vote on it. We know we have about 300 votes in favour.

“He can follow the Democrats: we have put our discharge petition on the board, get his members to sign this petition and again, support Ukraine. Or he could just get out of the way because we know that the American people are behind the Ukrainians.

“We know that each and every day that goes by is another day that Ukrainians are dying. We have members of the Ukrainian armed forces in my district, people who have lost legs, who have lost their vision, because they were standing in the breach … We’re fighting hard for this, Mr Speaker. Lead, follow or get out of the way.”

Other Democrats who spoke to reporters included army, navy and air force veterans with service in Iraq and Afghanistan, and Senator Richard Blumenthal of Connecticut.

All saluted Ukrainian courage. More than one called the Ukrainians “MacGyvers”, an admiring evocation of their make-do-and-mend spirit with meagre supplies, arising from a cult 1980s TV series starring Richard Dean Anderson.

The press conference in the House Triangle was staged in conjunction with Vote Vets and introduced by Alexander Vindman. A former US soldier of Ukrainian heritage, Vindman and his brother Eugene helped blow the whistle on Trump’s attempts as president to extract political dirt from Ukraine, prompting his first impeachment. Both were pushed out of the military. Eugene Vindman is now running for Congress in Virginia.

Representing Vote Vets, Rick Harris, the father of Thomas Gray Harris, a former US marine killed in Ukraine, said: “It is hard to have lost my son but I am proud of what he did. If he were here today, though he would use much more colourful language than me, he would tell the speaker to call the vote now.”

Dan Goldman of New York was not the only speaker to say Ronald Reagan, the Republican president revered in his party for standing up to Moscow, would be “rolling in his grave if he knew his party was not supporting democracy against Russia”. Vote Vets unveiled a new ad, featuring Reagan saying “democracy is worth dying for” and set to be broadcast on Fox News.

On Tuesday the Republican leader in the Senate, Mitch McConnell, told reporters Johnson should “let the House speak”. Asked about Republican proposals to offer aid to Ukraine as a loan not a grant, McConnell said it was more important to act quickly.

“The only way to get relief to the Ukrainians and the Israelis quickly is for the House to figure out how to pass the Senate bill,” he said, adding: “We’ve got a bill that got 70 votes in the Senate. Give members of the House of Representatives an opportunity to vote on it. That’s the solution.”

Also on Tuesday, the White House said the US would send Ukraine aid worth $300m, the first such move in months. Biden’s national security adviser, Jake Sullivan, said the funds came from unanticipated savings from Pentagon contracts and would be used for artillery munitions.

“This ammunition will keep Ukraine’s guns firing for a period but only a short period,” Sullivan said. “It is nowhere near enough to meet Ukraine’s battlefield needs and it will not prevent Ukraine running out of ammunition.”

US officials have also looked at options for seizing $285bn in Russian assets immobilised in 2022, then using the money to pay for weapons for Ukraine.

Also on Tuesday, Biden met the president and prime minister of Poland, to talk about Ukraine. On Capitol Hill, US intelligence agency chiefs pressed House members, saying new Ukraine aid would also discourage Chinese aggression.

The Ukrainian president, Volodymyr Zelenskiy, told French media Kyiv had improved its strategic position despite shortages of weaponry, but suggested the situation could change again if new supplies were not forthcoming. He also said Russia was preparing a new offensive for late May or summer.

Zelenskiy has said 31,000 Ukrainian soldiers have been killed in the two-year war.