UPDATE 2-U.S. Senate Democrats agree to $3.5 trln for budget reconciliation bill

(Adds details throughout, comment from Senator Sanders)

By Richard Cowan and Susan Cornwell

WASHINGTON, July 13 (Reuters) - U.S. President Joe Biden's drive for big new infrastructure investment got a boost on Tuesday when leading Senate Democrats agreed on a $3.5 trillion investment plan they aim to include in a budget resolution to be debated soon, Senate Majority Leader Chuck Schumer said.

"We have come to an agreement," Schumer told reporters after more than two hours of closed-door talks that included Senate Budget Committee Democrats and White House officials. Republicans have not been part of these negotiations.

"You add that to the $600 billion in a bipartisan plan and you get to $4.1 trillion, which is very, very close to what President Biden has asked us for," Schumer said.

Schumer was referring to work being done on a separate, bipartisan infrastructure bill totaling $1.2 trillion, of which nearly $600 billion would be new spending. This bill would finance the rebuilding of roads, bridges and other traditional infrastructure, as well as expand broadband internet service to many rural parts of the United States.

Democratic and Republican negotiators on the bipartisan measure also reported progress late in the day.

Schumer said the $3.5 trillion agreement, which still must be endorsed by the 50-member Senate Democratic caucus, would include a significant expansion of the Medicare healthcare program for the elderly - a top goal of Budget Committee Chairman Bernie Sanders.

Included in the Medicare expansion, Schumer said, will be coverage for dental, hearing and vision healthcare.

Further details were expected on Wednesday.

Biden will travel to Capitol Hill on Wednesday, Schumer said, to have lunch with Senate Democrats and discuss the difficult road ahead for advancing the emerging legislation.

Senator Mark Warner, a moderate Democratic member of the budget panel, said the agreement includes provisions to fully pay for the $3.5 trillion in infrastructure spending, but he did not elaborate.

The Senate's 50 Republicans are not expected to back the broader infrastructure effort, likely leaving Democrats to pursue passage on their own under a budget "reconciliation" process that sidesteps a rule requiring at least 60 votes to advance legislation in the 100-member chamber.

Biden has been seeking an increase in taxes on corporations and the wealthy to help fund the initiatives.

While the Senate Democrats did not detail the tax increases that would be part of this effort, Sanders said: "The wealthy and large corporations are going to pay their fair share of taxes so that we can protect the working families of this country."