The longest-ever United States Government shutdown appeared headed to an eventual resolution, after several Democratic Senators broke ranks to join Republicans in advancing a compromise deal – sparking an intra-party backlash.

Since October 1, the first day of the shutdown, more than a million federal workers have been unpaid, while government benefits and services have been increasingly disrupted.

Severe impacts on air traffic have begun to mount in recent days, with more than 1000 flights cancelled daily, raising the political pressure to end the stalemate.

“We’ll be opening up our country very quickly,” US President Donald Trump told reporters in the Oval Office, adding: “the deal is very good”.

After clearing a key procedural hurdle, the Senate began the voting process this afternoon NZT to pass the compromise budget measure.

It would then move to the House of Representatives, which like the Senate is controlled by Republicans. The chamber could vote on the bill as early as tomorrow to send it to Trump’s desk.

US Speaker of the House Representative Mike Johnson (centre) speaks during a news conference with the House Republican leadership on reopening the government at the US Capitol. Photo / Getty Images

“It appears to us this morning that our long national nightmare is finally coming to an end, and we’re grateful for that,” House Speaker Mike Johnson told reporters.

“At least some Democrats now finally appear ready to do what Republicans and President Trump and millions of hardworking American people have been asking them to do for weeks.”

The House – which Johnson has kept out of session throughout the standoff – would be called back this week, he said.

“I’d like to vote tonight after the Senate is done, but it takes everybody a while to get back” for a vote, Johnson told broadcaster CNN.

At the heart of the impasse is Democrats’ demand to extend health insurance subsidies expiring at the end of the year. Republicans insist any negotiation occur after the Government is re-opened.

Millions of Americans who have purchased health insurance through the “Obamacare” programme would see their costs double if the subsidies are not extended.

Yesterday’s breakthrough agreement would re-open the Government into January, with some programmes funded for the full fiscal year, and reverse some of the Trump Administration’s firings of federal workers.

The shutdown, starting October 1, left over a million federal workers unpaid and disrupted services. Photo / Getty Images

The bill notably would restore funding for the Snap food aid programme, which helps more than 42 million lower-income Americans pay for groceries.

While the Senate’s Republican leadership has agreed to hold an eventual vote on healthcare, it does not ensure the insurance subsidies will be extended.

“After 40 days of uncertainty, I’m profoundly glad to be able to announce that nutrition programmes, our veterans, and other critical priorities will have their full-year funding,” Senate Majority Leader John Thune said.

While leaders were rushing to move the Bill through Congress, it could still take days to make its way to Trump’s desk. Tomorrow is a national holiday.

Senator Jeanne Shaheen, one of eight Democratic caucus members who backed the measure, said the Senate “took a big step forward towards protecting the healthcare of tens of millions of Americans”.

Senator Jeanne Shaheen. Photo / Getty Images

She said the agreement would grant Democrats, despite being in the minority, the power to call a vote on healthcare legislation.

However, with the extension of the subsidies not guaranteed, the move has angered party members who preferred to keep holding out.

“Pathetic,” California Governor Gavin Newsom posted on X in reaction to the announced agreement.

Top Senate Democrat Chuck Schumer voted no, saying he could “not in good faith” support a measure “that fails to address the healthcare crisis”.

“This fight will and must continue,” he vowed.

Some lawmakers criticised Schumer himself for failing to keep the Democrats united.

“Tonight is another example of why we need new leadership,” Massachusetts Representative Seth Moulton said yesterday.

-Agence France-Presse