The Carter administration dispatched its top brass to Capitol Hill yesterday to fight the closing skirmishes in the battle for votes on the controversial Panama Canal treaties.

At the end of a hectic day of lobbying, headcounting and announcements by previously undecided senators, the fate of the first treaty - scheduled for a final vote tomorrow - remained uncertain.

The best available counts suggested that if the remaining handful of undecided senators split about evenly, the treaty should carry by two-thirds plus one or two votes. But no treaty supporters would predict confidently that this will happen.

Vice President Mondale, Secretary of State Cyrus R. Vance. Defense Secretary Harold Brown and other senior administration officials were in the Capitol yesterday to press the administration's case.

A new issue emerged yesterday and led one previously firm treaty supporter to question his own earlier decision to vote yes tomorrow. The issue was whether the White House has improperly offered political favors to undecided senators to try to influence their votes on the canal treaties.

Sen Bob Packwood (R-Ore.) said he was "troubled by the fact that so many rumors are rampant" about deals between the adminstration and undecided senators. He said the president should not be "master of ceremonies at 'Let's Make a Deal.'"

Packwood referred to a New York. Times article published yesterday that suggested that the White House had Panama Canal treaty votes in mind when it decided earlier in the week to buy substantial quantities of copper for strategic stockpiles, and when it decided not to oppose a farm bill backed by Sen. Herman E. Talmadge (D-Ga).

The article suggested that these moves were meant to help win over Talmadge and Sen. Dennis DeConcini (D-Ariz), a supporter of much greater government copper vurchases, to the canal treaties.

Talmadge and Sen. Sam Nunn (D-Ga.) announced their support for the treaty yesterday. Asked if the White House position on his farm bill had come before or after his decision, Talmadge said he didn't know what the White House position was.

However, sources in the Department of Agricutlure suggested that the administration did have Talmadge's canal vote in mind when it 'decided not to oppose his farm bill.

Several senators said privately that if this was the adminstration's intention, it misunderstood Talmadge and what would influence him.

DeConcini said it was ridiculous to think the copper decision would influence his vote, since he felt it was any inadequate program of purchases. He said he had told the White House that peripheral issues would not influence his canal vote.

Sen. Edward W. Brooke (R-Mass.) has told Senate associates that he felt President Carter had made a rather crude offer to win his vote for the canal treaties at a private meeting last week, according to informed sources. Details of the alleged offer were not revealed, and Brooke's office declined comment.

White House press secretary Jody Powell said yesterday that allegations of deals for senators' votes were unfounded. "I don't know of any trades on the Panama Canal treaties," Powell said. "I suppose it depends on what you call a trade."

Other senators talked in the cloak-rooms about this issue yesterday, many tending to believe that the White House was going out of its way to be nice to wavering senators, but none besides Packwood questioned the propriety of this openly. In the past, many senators have regularly, though privately, criticized the Carter White House for failing to make political deals with them.

Sen. Daniel P. Moynihan (D-N.Y.) said yesterday he had at least gotten a Cuban cigar out of Mondale. Moynihan was an early supporter of the treaties, and said he hoped the president wouldn't forget that the first supported was just as important as the 67th.

Apparently the last remaining undecided senators as of last night were: Henry L. Bellmon (R-Okla.), Brooke, Wendell H. Ford (D-Ky.), Paul G. Hatfield (D-Mont.), Jennings Randolph (D-W.Va.) and Edward Zorinsky (D-Neb.).

Deconcini said he would vote yes, provided the administration accepts a reservation he proposes that would allow the United States to use Military force in Panama unilaterally after 2000 to keep the canal open if it is closed for any reason. DeConcini is scheduled to meet with Carter at 9 a.m. today to discuss this reservation, which is expected to annoy Panama.

An aide to DeConcini predicted that the White House will accept the reservation if it feels it needs DeConcini's vote.

Yesterday, Sens. Richard S. Schweiker (R-Pa.) and William V. Roth Jr. (R-Del.) announced their opposition to the treaties. Besides Nunn and Talmadge, Sens. John C. Danforth (R-Mo.) and H. John Heinz III announced they would vote would be conditioned on the approval of three reservations, but an administration official said all three would be acceptable.

The possibility remained of parliamentary confusion in the last two days of scheduled debate on the first treaty." Treaty opponent James B. Allen (D-Ala.) hinted last night that he might try to disrupt the Senate leadership's timetable, but what his intentions are was not clear.

Yesterday the senate failed to vote on a Nunn reservation to the final resolution of ratification that would allow continued basing of U.S. forces in Panama after 2000, provided both countries agree to that. Nunn's is one of 19 pending amendments to the final resolution of ratification, and all are theoretically supposed to be dealt with by 4 p.m. tomorrow, when the final vote is scheduled.