Democrats in the US Senate have taken the first step toward fast-tracking President Joe Biden's proposed $US1.9 ($A2.5) trillion coronavirus aid bill without Republican support.
The Senate voted along party lines on Tuesday, with Democrats edging out Republicans 50-49, to open debate on a fiscal 2021 budget resolution with coronavirus aid spending instructions.
Using this strategy unlocks a legislative tool needed for Democrats to enact Biden's package in the face of opposition.
Republicans have pushed back on Biden's $US1.9 trillion price tag, which follows $US4 trillion in COVID-19 aid last year.
The president told Democratic senators in an online luncheon meeting on Tuesday that although he was willing to make some modifications to his proposal, a Senate Republican counter-proposal was inadequate.
On Monday, Biden met with 10 Senate Republicans to discuss their scaled-back $US618 billion plan.
"He said he told Senate Republicans the $600 billion that they proposed was way too small," Senate Majority Leader Chuck Schumer told reporters.
"We're off to a totally partisan start," Republican leader Mitch McConnell said.
The pandemic has killed nearly 444,000 people in the United States.
Jared Bernstein, a member of the White House Council of Economic Advisers, said on Tuesday the Republican proposal fell far short in a number of areas, including funding to reopen schools.
Republicans called for spending $US20 billion on schools, compared with Biden's proposal for $US170 billion.
"We think that's what it's going to take to reach people," Bernstein told CNN.
Biden's package faces a potential Republican roadblock in the 100-member Senate, which is divided 50-50 but requires a 60-vote threshold to pass most legislation.
The budget resolution, if approved by the House of Representatives and Senate, would activate a legislative tool called reconciliation, allowing for Senate passage with 51 votes that would include 48 Democrats, two independents who caucus with them, and Vice President Kamala Harris.
Republican Senator Patrick Toomey was absent for the vote.
His office said he was delayed by bad weather. Toomey's absence meant Harris was not needed to cast her first tie-breaking vote on Tuesday.
If the measure passes both chambers it would mark the first time congressional Democrats had used the manoeuver to flex their legislative muscle since winning razor-thin control of the Senate in two run-off elections last month in Georgia. They already controlled the House.