Sen. Cla'borne Pell (D-R.I.) and Rep. John Brademas (D-Ind.), chairmen of the subcommittees that handle cultural policy on Capitol Hill, said they were informed yesterday that President Carter will nominate Livingston Biddle as the new chairman of the National Endowment on the Arts.

They were among a number of people, including members of the National Council on the Arts, telephoned yesterday by members of the White House staff with the news that the President had accepted Biddle the choice of a five-member search committee.

Biddle, an aide to Sen. Pell on education and cultural matters and a former deputy chairman of the Endowment, could not be reached for comment. It was learned that he met with the President on Monday.

Pell, a friend and college roommate of Biddle, said that he was "absolutely delighted" and that Biddle "is the most qualified person for the job."

Brademas, in a statement, cited Biddle's "extensive experience in dealing with the Endowment, which will enable him to do an outstanding job as its new chairman. This is combined with his own personal commitment to an important place for the arts in American life. I compliment President Carter on his choice."

The White House declined to confirm or deny that a nominee had been chosen. Instead, a spokesman issued this statement: "There will be no announcement at this time concerning the new chairman. We expect that the President's nomination for this post will be forwarded to the Senate in time for consideration at this session, to ensure continuity at the National Endowment on the Arts."

Congress ends its current session this month. It is belived that no formal announcement on the chairmanship will come from the White House until FBI and conflict-of-interest checks are made.

Biddle was one of 10 persons considered by the selection committee for the $52,000-a-year post.

The Endowment has been run by its deputy director, Michael Straight, since chairman Nancy Hanks' second four-year term expired last weekend.