After months of delay and increasingly dire warnings, the US House of Representatives approved $61bn in new aid to Ukraine by a comfortable margin.

The passage is a big win for Ukraine, which has been desperate for new military supplies to stave off a Russian offensive that is gaining ground.

The US Pentagon press secretary told reports on Thursday that US military supplies, including for air defence systems and artillery units, could be moved to Ukraine in a matter of days after final approval.

Saturday's rare moment of co-operation in Congress is also a cause for celebration for President Joe Biden, who has been calling the Ukraine war a world-defining conflict that the US cannot afford to shrug off.

"Today, members of both parties in the House voted to advance our national security interests and send a clear message about the power of American leadership on the world stage," he said.

The president could sign the aid into law later this week, as the US Senate is expected to approve the House foreign aid package - which also includes funding for Israel and Taiwan - as early as Tuesday.

Republican Speaker of the House Mike Johnson also has reason to be encouraged by the result. It was his change of heart on Ukraine support, from a reticence to active support, that proved the decisive factor in getting the foreign aid package approved.

He received a vote of confidence from Donald Trump just a week ago, and the former president - who has spoken out against more support for Ukraine in the past - could have caused untold headaches for Mr Johnson as aid moved through the House. Instead, he largely stayed silent, focused instead on his ongoing trial in New York City.

Mr Johnson may still pay a political price for Saturday's achievement, however. He relied heavily on Democratic support not just on the final votes but to clear procedural hurdles leading up to those votes.

His decision to turn to Democrats was necessitated by intense resistance among a handful of Republicans, some in key positions of power in the House, who opposed any new aid to Ukraine. Now those Republicans may force a vote on whether to oust Mr Johnson from the speaker's chair.

In remarks to the press after passage of the foreign aid bill, Mr Johnson defended his actions and said he was not walking around the halls of Congress worrying about being removed from power.

"I've done here what I believe to be the right thing," he said.

While a move to trigger his ouster did not come on Saturday, three Republicans have come forward to call for Mr Johnson's removal - and they say more will join them in the coming days, as the House breaks for a week-long recess.

"I'm actually going to let my colleagues go home and hear from their constituents," Republican Congresswoman Marjorie Taylor Greene of Georgia, who drafted a resolution to remove Mr Johnson weeks ago, said after the foreign aid package was approved.

Public opinion polls have shown many Republican voters souring on additional aid to Ukraine, even as Democrats and independents support American help in the war effort.

If a removal vote does come, some Democrats have expressed a willingness to back the speaker - essentially rewarding him for standing up to members of his own party to ensure Ukraine aid, a high priority for Democrats and the Biden White House, cleared the House.

That could give Mr Johnson a short-term lease on political power, but it is difficult to imagine how a Republican speaker can reliably count on ongoing Democratic support. While there was overwhelming bipartisan backing for this foreign aid package, at some point Mr Johnson will push legislation on an issue that angers Democrats.

If his Republican critics make another move then, he may find his former allies across the aisle are much less willing to throw him a lifeline.

For now, however, Mr Johnson can savour a hard-fought victory. His strategy - to break the aid package into individual components on Ukraine, Israel and Taiwan and to face down his Republican opponents who openly defied him - worked largely as planned.

In his remarks after the votes, he said the legislation was not perfect, and that it was not a "blank cheque" - a reflection that recent months have shown there are clear and growing limits to US support.

He said new aid must be monitored to ensure that it is being spent wisely and Ukraine must find an "endgame strategy" for the war. But he stood by the path he took to arrive at Saturday's result.

"I've said before, you do the right thing and you let the chips fall where they may," Mr Johnson said.

For a legislator who languished in relatively obscurity until a leadership crisis last October pushed him into the spotlight, it is a historic achievement. But the coming weeks will determine whether it will also be his political epitaph.