US President Joe Biden has secured a deal on an infrastructure package worth about $1tn to spend billions of dollars to upgrade roads, bridges and broadband networks over the next eight years.

The agreement with a bipartisan group of senators falls short of the $2.3tn infrastructure spending plan announced by Biden in March and does not address the $1.8tn in social safety-net spending that the US president proposed in April.

But it represents a big milestone for Biden, who vowed to use his decades of experience as a senator from Delaware to work with Republicans and defy the polarisation that has become endemic to US politics.

Biden announced the agreement at the White House on Thursday after meeting the moderate senators who forged the compromise, including Kyrsten Sinema, the Arizona Democrat, and Susan Collins, a Republican senator from Maine.

“We made serious compromises on both ends,” the president said, adding it reminded him “of the days we used to get an awful lot done in Congress”.

Democrats and the White House hope to approve the rest of their economic agenda using their slim majorities in Congress separate from the bipartisan infrastructure bill negotiated with Republicans.

But Nancy Pelosi, the House Democratic speaker, said on Thursday that the legislation would have to be linked: the lower chamber of Congress would only consider the bipartisan infrastructure package if Biden’s broader economic priorities — including tax increases on corporations and the wealthy — had first passed the Senate.

Biden has cast the infrastructure bill as crucial to redressing the chronic underfunding of US transportation networks and other facilities over the years, and placing America in a better position to compete with China in the 21st century.

“There’s massive investment going on with the autocrats,” he said in remarks from the White House later in the afternoon. “We have to move and we have to move fast.”

A large-scale infrastructure agreement had been a goal of Republicans and Democrats, even during Donald Trump’s presidency, but had been elusive. Biden said he had been flexible in the negotiations and was unlikely to make further demands.

“They have my word, I’ll stick with what they’ve proposed. And they’ve given me their word as well. Where I come from that’s good enough for me,” Biden said.

Some members of the bipartisan group celebrated the agreement. “It’s infrastructure week!” tweeted Bill Cassidy, the Republican senator from Louisiana.

The agreement on infrastructure, if passed by Congress, would come on the heels of Biden’s $1.9tn stimulus bill, which was approved in March as an emergency measure to stoke the recovery as the country emerges from the pandemic.

The White House said the proposed deal involved $579bn in new spending; when combined with the renewal of existing funding for infrastructure, the total would come to $973bn over the next five years, and $1.2tn over the next eight years.

The new spending would include $109bn on roads and bridges, $66bn for rail networks and $49bn for public transit. Ports, airports and electric vehicle charging stations would also get extra funding.

The biggest source of tension over the infrastructure package related to disagreements over ways to raise revenue so that it did not add to the deficit.

In the end, the bipartisan group agreed to cover the cost with unspent money from previous rounds of pandemic-related stimulus measures, an increase in the Internal Revenue Service’s capacity to enforce tax laws, and sales from the Strategic Petroleum Reserve.

Republicans had proposed increasing the federal petrol tax and user fees for electric vehicles in order to pay for the plan, but the White House rejected the idea because it would violate Biden’s pledge not to increase levies on Americans earning less than $400,000 per year.