WASHINGTON (Reuters) - A senior White House adviser said on Sunday that Democrats will be disappointed as the party trims President Joe Biden's agenda to fit political realities on Capitol Hill, but vowed two major pieces of legislation in the package would become law.

"People will be disappointed. People will not get everything they want, that is the art of legislating, but the goal here is to get both bills, and we're going to fight until we get both bills," Cedric Richmond, director of the White House Office of Public Engagement, said on NBC's "Meet the Press."

Biden visited the Capitol on Friday to try to end a fight between moderates and progressives in his Democratic Party that has threatened the two bills that make up the core of his domestic agenda - an infrastructure bill and a multi-trillion-dollar social spending bill.

Moderate Democratic lawmakers have sought an immediate vote on a $1 trillion infrastructure bill in the House of Representatives that has already passed the Senate, while progressives have sought to wait until there is agreement on sweeping legislation proposed at $3.5 trillion, to bolster social spending and fight climate change.

Biden, a former senator, told Democrats they could delay a vote on the smaller bill and scale back the larger one to around $2 trillion, according to aides and lawmakers.

The influential chair of the Congressional Progressive Caucus, Representative Pramila Jayapal, said on Sunday an acceptable range for her for the social spending bill would be somewhere between $1.5 trillion and $3.5 trillion.

Moderate Democratic Senator Joe Manchin has said his top line for the package is $1.5 trillion, but Jayapal told CNN: "That's not gonna happen. Because that's too small to get our priorities in. So, it's gonna be somewhere between 1.5 and 3.5 (trillion dollars)."

Progressive Democratic Senator Bernie Sanders, chairman of the Senate Budget Committee, told ABC News Sunday that $3.5 trillion "should be a minimum. But I accept there is going to have to be give and take."

The Senate's number two Democrat, Richard Durbin, told CNN he had supported $3.5 trillion but "concessions will be made, we're certain of that."

(Reporting by Susan Cornwell; Editing by Scott Malone and Diane Craft)