Intense efforts to rescue the Panama Canal treaties continued yesterday, but the Carter administration and key Senate proponents failed to find a formula that could please both two-thirds of the Senate and the Panamanians.

The negotiations continued to center on Sen. Dennis DeConcini (D-Ariz.), who may be the key to passage or rejection of the treaties.

DeConcini told reporters yesterday that he did "not see the need" to add a new understanding to the second canal treaty reiterating that the United States does not seek the right to intervene indiscriminately in Panama's internal affairs.

The freshman senator said he would have to see "powerful or overpowering evidence" that such a new addition was needed before he would approve it. But he added, "I don't want to shut the door."

The Carter administration and senators leading the fight for treaty ratification believe they must get some change in the treaties - "something to soothe the Panamanians," as one source put it - to avoid Panamanian rejection of the treaty package.

There were signs of strain in the pro-treaty coalition yesterday. For one, Sen. Howard H. Baker Jr. (R-Tenn.), the minority leader and a crucial member of that coalition, disassociated himself from the DeConcini flap, saying, "The problem is on the Democratic side. I don't know what is going on."

Several sources said they saw signs that the majority leader, Robert C. Byrd (D-W. Va.), was feeling "disgusted" with the ongoing uncertainties over the fate of the treaties, as one of his colleagues put it, and might also be feeling that it was now the Carter administration's problem to find a way out of the current difficulty.

The feeling is widespread in the Senate that the administration got itself into the current jam by accepting the orginal DeConcini reservation knowing that the Panamanians regarded it as unacceptable.

Several senators, including Daniel Patrick Moynihan (D-N.Y.) and Floyd K. Haskell (D-Colo.), threatened to reverse their "aye" votes for the first treaty if the administration went too far to satisfy DeConcini and strayed from the traditional American Position against intervening in other countries' affairs.

DeConcini insisted yesterday that his reservation to the first treaty, approved by the Senate last month, said nothing about interfering in Panama's affairs, so he saw no need to clarify it.

The reservation declared that the United States would retain the right to use military force unilaterally in Panama to keep the canal open. In a floor speech when introducing the reservation, DeConcini said he wanted it clear that if labor unrest in Panama or something of the kind closed the canal, the United States could use force to reopen it.

DeConcini's principal legislative aide has said several times that this reservation spelled out a limited right of intervention in Panama.

DeConcini met for an hour yesterday with Deputy Secretary of State Warren M. Christopher. They apparently agreed on acceptable language for a second reservation that DeConcini wants to add to the second treaty, which spells out terms of the transfer of the canal to Panamanian control in 2000.

In this reservation DeConcini wants to add an explicit statement that U.S. forces stationed in Panama until 2000 will have the "primary" role in defense of the canal, and that in case of any dispute the Panamanians cannot veto U.S. action.

But this is a secondary concern to the administration, which is much more worried about getting DeConcini at least to go along with some reaffirmation of the principle of non-interference in the second treaty. The senator was supposed to discuss this with President Carter yesterday, but the meeting was cancelled Tuesday night when both sides agreed that they were too far apart to make a session with the president worthwhile.

Though there are no head counts confirming their hunch, administration lobbyists and Senate proponents agree that any statement on nonintervention needs DeConcini's support or crucial votes on final passage (probably including DeConcini's) could be lost. The first treaty carried with one vote to spare.

A key Senate leader predicted last night that there will be no attempt to resolve the present difficulty until Monday or Tuesday. "We haven't lost a single vote yet," this Senator said, "and its quite possible we can stay in that position."

Another leader of the pro-treaty bloc said that a solution will not require "an act of wizardry," but rather "an act of draftsmanship" to find language pleasing to all concerned.