Majority Leader Robert C. Byrd (D-W. Va.) will propose to his colleagues today that the Senate begin meeting from noon until 8 or 9 p.m. to debate the Panama Canal treaties, leaving more time for Senate committees to do their work.

This is the first concrete sign that the treaty debate, now nearly three weeks old, is disrupting other Senate business. The leadership is nervous that prolonged debate will make it difficulty, if not impossible, to meet deadlines set by law for the budget-making process.

Byrd has been denying permission to Senate committees to meet beyond brief morning hours during the treaty debate thus far. Several committees have had to abandon hearings or drastically curtail them as a result.

Vice President Mondale met with Byrd in the Capitol yesterday to discuss the treaty debate, and said afterward that the debate was moving very slowly. Mondale declined to accuse treaty opponents of filibustering, but said their tactics "will undermine support for them" if they are continued.

"We want action," Mondale said. "The American people want action."

Byrd plans to emphasize the point by cutting short the Senate's easter recess, now scheduled to last 10 days --the Monday after Easter Week. Byrd proposes instead to give the Senate two days off -- Good Friday and Easter Monday.

Minority Leader Howard H. Baker Jr. (R-Tenn.) said yesterday he thought it would take a perceptible reaction from the public to speed up the canal treaty debate. Baker, who has emerged as a principal proponent of the treaties, said he thought time was on their side.

Two weeks ago, he noted, treaty proponents were afraid they might not be able to beat back opponents' efforts to amend the treaties, but now they are regularly beating all amendments by 2 to 1.

The Senate defeated two more proposed amendments by nearly that margin yesterday. One, proposed by Sen. James B. Allen (D-Ala.)# would have permitted the U.S. president to prolong the U.S. military presence in Panama by 20 years if he determined that Panama was under foreign or Communist domination in 1999, when the treaties envisage turning the canal over.

The factor adding time to the debate, several senators have noted, is the fact that the entire proceeding is being broadcast by National Public Radio. This makes the debate "an educational process," as one senator put it, and treaty proponents who might ordinarily let the opponents make their speeches unchallenged feel they must stand up and answer them for the radio audience.