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US senators passed a $1.2tn spending bill in the early hours of Saturday morning to avert a partial government shutdown, capping a budgetary stand-off that threatened to close non-essential operations of some federal agencies.

The bill’s progress in the upper chamber of Congress, which is controlled by Democrats, followed a tumultuous passage of the legislation in the House of Representatives, which is led by Republicans, on Friday.

The agreement was welcomed by the White House, which said that President Joe Biden would sign the bill on Saturday.

Although the House approved the spending bill with broad bipartisan support, it triggered a backlash from allies of Donald Trump within the Republican party who objected to the compromise.

Marjorie Taylor Greene, the firebrand congresswoman from Georgia, launched a bid to oust Mike Johnson, the speaker of the House, who has only been in the job since October. Greene did not say when she intended to follow through on the threat, but called it a “warning” for Johnson.

The agreement in the Senate involved allowing Republicans in the upper chamber a vote on a series of amendments — including some tied to tightening immigration laws — as they try to use the surge in border crossings as a political weapon against Democrats in the 2024 election. Democrats had been resisting the pressure to allow the amendments.

“Senate Democrats are shutting down the government rather than allow us to vote on things like deporting criminal migrants. Say what you will, but they’re committed to open borders,” JD Vance, the Ohio senator close to Trump, wrote on X before the deal was reached.

The agreement on the spending bill will keep the government funded until the end of September. It sets the stage for a bigger battle in the coming weeks over the fate of aid to Ukraine, Israel and Taiwan, as well as humanitarian assistance in Gaza, which has been stalled in Congress.

Although the Senate passed the national security package backed by the White House this year, it has languished in the House, where Johnson has resisted putting it up for a vote under pressure from Ukraine aid sceptics within his party — and Trump.

Lindsey Graham, the Republican senator from South Carolina, has been floating a plan to offer Ukraine a loan instead, which some Democrats are warming to as a last resort. But most supporters of Kyiv in Washington are still hoping for a breakthrough on the aid package.

But Greene’s threat to Johnson’s speakership could complicate the effort to secure Ukraine aid since she is a staunch opponent of helping Kyiv.

Meanwhile, Johnson’s majority in the House of Representatives looks set to narrow to just one vote, after Mike Gallagher, the Wisconsin Republican who has chaired the House select committee on China, said he would resign from his seat on April 19.