Washington — With President Biden set to leave Washington for a trip to Europe later this week, Democratic leaders on Capitol Hill are racing to broker an agreement on his multi-trillion-dollar social spending package and settle splits among their conference over paid leave, an expansion of Medicare benefits and the means of paying for the legislation.House Democrats met behind closed doors Tuesday amid the ongoing negotiations over a framework for Mr. Biden's proposal to expand a slew of social programs, and the president is poised to huddle with lawmakers at the White House to discuss moving his domestic policy agenda forward, White House press secretary Jen Psaki said.But divisions remain among Democrats over key aspects of the legislation, complicating Democratic leaders' goals of reaching a deal on the details of the package before Mr. Biden leaves the country to attend a Group of 20 conference in Rome and a United Nations climate summit in Glasgow, Scotland, known as COP26. "This is an urgent moment to strengthen President Biden's hand on the world stage, and I understand and respect they have concerns that they're negotiating around, but to go to the G20 and to go to COP26 in Glasgow without progress on the deal would be to miss a critical opportunity," Democratic Senator Chris Coons of Delaware told reporters of his colleagues.To address concerns from moderate Democratic Senators Joe Manchin of West Virginia and Kyrsten Sinema of Arizona, whose support for the plan is crucial for passage in the Senate, party leaders have already scaled down the measure's price tag from $3.5 trillion to roughly $2 trillion over 10 years. Mr. Biden also said last week his plan for free community college is likely to be stripped from the package, and a proposal for 12 weeks of paid family leave may be trimmed to four weeks.While key pieces of the plan are being scaled down or removed altogether, the White House and Democratic leaders are urging lawmakers to back the package, arguing they should seize the opportunity to pass what party leaders say is "transformational legislation." House Speaker Nancy Pelosi is set to meet Tuesday afternoon with Congresswoman Pramila Jayapal of Washington, the chair of the Congressional Progressive Caucus, to discuss the plan, according to a Democratic aide."The alternative to what is being negotiated is not the original package, it is nothing," Psaki told reporters during the White House press briefing. "So what we're really facing right now is a question of whether people are going to support the largest investment in climate and clean energy. Do they want to be part of the largest investment in early childhood education in history? Do they want to make health care more affordable and accessible? Or do they want to let the perfect be the enemy of the historic?" Still, Democrats remain at odds over other aspects of the sweeping plan, including an expansion of Medicare to cover dental, vision and hearing. Manchin has expressed concerns over the solvency of the program, and Mr. Biden said during a CNN town hall last week that the West Virginia senator opposes expanding Medicare. But Senator Bernie Sanders of Vermont, an independent who votes with the Democrats, told reporters on Capitol Hill that the package must include the program's expansion."Any reconciliation bill must include serious negotiations on the part of Medicare with the pharmaceutical industry, lower the cost of prescription drugs. That's what the American people want," he said. "Any serious reconciliation bill must include expanding Medicare to cover dental, hearing aids and eyeglasses."Manchin also opposes some of the climate provisions contained in the package, and he scuttled a proposed $150 billion "clean energy performance program," which would pay utility companies that increase their renewable energy supplies by 4% per year.Still, the West Virginia senator has projected optimism that Democrats could reach an agreement on the framework for their social spending plan this week, though the senator reiterated Monday that he backs a price tag of $1.5 trillion, lower than Mr. Biden's proposed topline figure of around $2 trillion.The Senate Finance Committee is expected to roll out Wednesday a proposal for a tax on billionaires to raise revenue to pay for the social spending plan after Sinema came out against raising taxes on corporations and the wealthiest Americans. But House Ways and Means Committee Chairman Richie Neal expressed skepticism Monday about the billionaires tax. Still, Senate Majority Leader Chuck Schumer said in remarks on the Senate floor that Democrats are making "important progress" toward finalizing Mr. Biden's domestic policy plan."We remain confident that a final deal is within reach," he said.Psaki, though, said Mr. Biden could also continue negotiations with Democrats while he is in Europe.Zak Hudak, Alan He and Jack Turman contributed to this report.