Senate Democrats were pressing early Saturday toward approval of their first budget blueprint in four years, a political milestone that would cap months of GOP criticism and set the stage for direct negotiations with the Republican-controlled House.

The Senate blueprint calls for nearly $1 trillion in new taxes over the next decade and only modest reductions in projected government spending. While it appears to have united most of the 55 senators who caucus with Democrats, it would do little to alter the nation’s financial outlook, permitting the portion of the national debt held by outside investors to swell from nearly $12 trillion today to more than $18 trillion by 2023.

House Republicans, by contrast, have adopted an anti-tax spending plan that would balance by 2023, leaving the national debt to top out at about $14 trillion. But the House budget, drafted by Rep. Paul Ryan (R-Wis.), calls for a radical reduction in the size of government by curtailing spending on dozens of programs for the poor, repealing President Obama’s health-care law and partially privatizing Medicare for people now younger than 55.

Neither of the budget plans will ever be put into effect. Instead, they set the extreme boundaries as Washington prepares to open a new chapter in the long-running debate over taxes and spending.

As soon as Friday evening, Senate leaders planned to request a formal conference on the budget with the House. That would establish Ryan, the former ­vice-presidential nominee who chairs the House Budget Committee, and Senate Budget Committee Chairman Patty Murray (D-Wash.) as lead negotiators for their respective parties heading into another potential showdown later this summer over the federal debt limit.

Obama has been busily courting Republicans, mostly in the Senate, with the promise that Democrats would back a more moderate path to deficit-reduction that pairs roughly $600 billion in new revenue with nearly $1 trillion in spending cuts, including structural changes to Medicare and Social Security, by far the most expensive federal programs.

On Friday, Murray expressed optimism about the road ahead.

“I realize there are serious differences between the parties, and the last few years have been especially polarized here in Congress,” she said in remarks on the Senate floor. “But the House has now passed its budget resolution, and we will be working here in the Senate to pass ours this evening. We have presented very different visions for how our country should work and who it should work for — but I am hopeful that we can bridge this divide.”

After Ryan’s budget narrowly passed the House on Thursday, with 10 Republicans joining every Democrat in voting against it, Ryan, too, pledged to “try to make divided government work.” But he has warned repeatedly that House Republicans will need significant concessions in the form of spending cuts or changes to entitlement programs before they will agree once again to raise the legal limit on government borrowing.

The debt-limit fight is not expected to reach a crescendo until August, and it was a distant worry Friday, as senators prepared to leave town for a two-week Easter break.

Before they could depart, however, they had to slog through the final stage of the arcane Senate budget process: a marathon of symbolic votes on potential amendments to the budget blueprint known as the “vote-a-rama.”

This year’s vote-a-rama technically began Thursday night, when Democrats forced Senate Republicans to vote on the Ryan budget (rejected 59 to 40, with five Republicans voting no) and Republicans forced Democrats to vote on balancing the budget over the next decade (rejected 53 to 46, with all but one Democrat voting no).

The Senate also overwhelmingly agreed, 79 to 20, that it would be a good idea to repeal an unpopular 2.3 percent tax on medical devices enacted to help finance Obama’s health-care legislation. On Friday, the Senate went on record, 62 to 37, in support of the Keystone Pipeline, which has been held up by the Obama administration because of environmental concerns. And senators signaled strong support, 75 to 24, for legislation to permit states to require online retailers to collect sales tax on transactions in their states, a move that could end tax-free shopping on the Internet.

Pessimists feared the vote-a-rama — which mainly featured partisan “message” amendments — would drag on into the wee hours, delaying both passage of the budget and senators’ departures until early Saturday. But optimists held out hope that party leaders would pull the plug by midnight.