Joe Biden landed in the UK for his first foreign trip as US president on Wednesday to great fanfare, kicking off a busy schedule that will include a meeting with UK prime minister Boris Johnson, the G7 summit in Cornwall and tea at Windsor Castle with Queen Elizabeth II.

But while “Hail to the Chief” ushered the president’s arrival at the RAF Mildenhall air base in Suffolk, lawmakers back in Washington were scrambling to salvage his sweeping infrastructure package after Biden called off bipartisan talks with Shelley Moore Capito, the Republican senator from West Virginia, following weeks of back and forth.

The collapse of the negotiations on the eve of Biden’s departure raised fresh questions about how his ambitious legislative proposals on matters including infrastructure, voting rights, gun reform and energy will become reality, with Democrats controlling both chambers of Congress by the slimmest of margins.

“One of the questions here is whether any of these bills can be modified to pick up Republican votes,” said Jim Manley, a former senior aide to Democratic senators Harry Reid and Ted Kennedy. “Compromise is never a dirty word . . . the issue here is whether that is going to be at all possible.”

The Senate’s 100 seats are split 50-50 between Democrats and Republicans, with vice-president Kamala Harris able to cast a tiebreaking vote.

But most bills must win support from at least 10 Republican senators in order to clear a 60-vote filibuster threshold to become law. Earlier this week, the Senate failed to advance a Democratic bill intended to narrow the gender pay gap after it did not receive the endorsement of a single Republican.

On infrastructure, the White House has said Biden would now turn his attention to working with a bipartisan group of eight senators — including Democrats Joe Manchin of West Virginia and Kyrsten Sinema of Arizona, and Republicans Mitt Romney of Utah and Bill Cassidy of Louisiana — to hash out a compromise with a goal of attracting the support of lawmakers in both parties.

The lack of bipartisan agreement prior to the president’s European tour is a disappointment for Democrats and the White House. Many on Capitol Hill remain sceptical that a deal can now be done, particularly when the two parties remain so far apart on both the size and the scope of any infrastructure package — not to mention how to pay for it.

Biden initially introduced a $2.3tn plan that would be funded largely by a rise in the corporate tax rate and higher taxes on the wealthiest Americans. Republicans have pushed for a more modest bill and drawn a “red line” against tax increases.

John Barrasso, the second most senior Senate Republican, on Tuesday said he thought it would be “very difficult” for Biden to secure the backing of at least 10 Republicans on any new deal.

Romney struck a more optimistic tone on Wednesday, telling reporters on Capitol Hill that “eight or nine” Republicans thought his group of negotiators was “on the right track”.

But Zac Petkanas, a Democratic strategist who also served as an aide to Reid, doubted enough Republicans would join any compromise to forge a bipartisan infrastructure bill.

“Eight or nine Republicans ain’t going to do it. Eight or nine Republicans is not 10 Republicans. Nobody has been able to say, ‘here are the 10 Republicans that would support this bill’.”

Jen Psaki, White House press secretary, on Wednesday said the president would continue to push for a deal, with his cabinet members engaging with lawmakers while he was overseas.

“[The president] is quite familiar with the fact that this process . . . takes some patience and time, that there are going to be moments where we are near death and then it comes back,” Psaki told reporters on Air Force One en route to the UK. “That is always how policymaking, lawmaking, billmaking happens.”

Biden has made clear he would prefer to accomplish at least part of his infrastructure plan through a bipartisan deal rather than using a Senate convention called reconciliation, which would enable certain legislation to advance with only Democratic support.

Chuck Schumer, the Senate’s top Democrat, acknowledged this week that reconciliation is an option if bipartisan talks fail — or that a separate reconciliation bill may be introduced after a two-party agreement is struck.

“It may well be that part of the [infrastructure] bill that will pass will be bipartisan, and part of it will be through reconciliation,” Schumer told reporters on Capitol Hill on Tuesday. “But we are not going to sacrifice the bigness and boldness in this bill. We will just pursue two paths and at some point they will join.”

Sceptics, however, point out that even the reconciliation route remains an uphill battle for Senate Democrats, given that a handful of moderate members of the party’s caucus, including Manchin and Sinema, routinely side with their Republican colleagues.

Manchin last weekend ruffled feathers in his own party with a newspaper column vowing to block a landmark voting rights bill. He has insisted it is too soon to break off bipartisan talks and push ahead with a Democrat-led reconciliation bill.

However, Manley said he expected Manchin to change his tune if the Senate cannot reach a breakthrough on bipartisan infrastructure talks and more measures fail on matters such as voting rights and gun control.

“Based on everything I have seen, a whole bunch of bills coming over from the House are about to die a slow, painful death in the Senate,” Manley said.