To avoid an unprecedented default, the United States Senate is expected to vote on Tuesday to raise the federal government's $28.9 trillion debt limit and send the bill to the House of Representatives for final approval.

Following a months-long standoff, both Democratic and Republican aides said the Senate would vote on passage later Tuesday. The chamber has allowed for up to ten hours of debate, which could cause the vote to be postponed until the evening.

It was unclear how long the debate would last or when the House would vote on the bill and send it to the White House for Democratic President Joe Biden to sign.

Democrats, who control the Senate and the House by a slim margin, have yet to reveal the magnitude of the increase. However, observers anticipate a $2 trillion to $3 trillion increase to meet the federal government's needs through next year's Nov. 8 midterm elections, which will determine congressional control.

The increase is required in part to cover debt incurred during Republican Donald Trump's presidency, when the debt increased by approximately $7.85 trillion, owing to sweeping tax cuts and spending to combat the COVID-19 pandemic.

Republicans on track to dash Democratic hopes of US Senate majority –

U.S. Treasury Secretary Janet Yellen urged Congress to raise the debt ceiling by Wednesday.

Republicans, who control half of the Senate, have attempted to tie the vote to Biden's $1.75 trillion "Build Back Better" bill, which aims to strengthen the social safety net and combat climate change.

The 48 Senate Democrats and two independents who caucus with them are likely to raise the debt ceiling on their own, with a tie-breaking vote from Vice President Kamala Harris, thanks to an unusual deal worked out by the top Democrat and top Republican in the Senate and approved by both chambers last week.

The debt ceiling debate and another self-inflicted crisis, passing a bill to fund the government through February, occupied much of Congress' time this month, and members in both chambers are now eager to begin long holiday recesses.

Since World War One, votes to raise the country's debt ceiling have been held on a regular basis. However, some lawmakers have become wary of such legislation in recent years, fearing voter backlash.