President Carter has addressed a veiled warning to Panama that its objections to Senate amendments to the first Panama Canal treaty could endanger passage of the second treaty.

Carter's voice joins a chorus of senators who are upset at Panama's public, but unofficial, expressions of unhappiness at a Senate-approved amendment giving the United States the right to intervene militarily to keep the canal open after it is taken over by Panama in the year 2000.

"I think any sort of a change or unpredictable development could endanger the passage of the second Panama Canal treaty in the Senate because it hangs like a thread," Carter said. "The support that we have is pretty tenous in some instances. . .

"Any statement, even if it is well-based, by the Panamanians that would cause consternation or doubt in the minds of U.S. senators could very well endanger the passage of the second treaty."

Carter made the remarks at a press conference Friday with visiting editors and broadcast executives. The text of the interview was released yesterday.

In a letter to the United Nations, Panama has protested an amendment to the first treaty sponsored by Sen. Dennis DeConcini (D-Ariz.). The amendment is formally known as a "reservation" since is an appendage to the treaty rather than an amendment to its body.

A spokesman for DeConcini said yesterday the senator will propose a similar reservation to the second treaty.

The first treaty, approved 68 to 32 last month, provides for neutrality of the canal after it is turned over to Panama. The second treaty, to be voted on April 18, provides for the United States to turn over the canal to Panama by 2000.

This is just doing the same thing for the second one as we did for the first," the spokesman said. "It's not logically consistent to say we can do it after the year 2000, when we will have no military presence in Panama, but not between now and then."

Deputy Secretary of State Warren Christopher visited DeConcini Friday, but the spokesman said he made no effort to dissuade the senator from offering the reservation. The aide said DeConcini will vote against the treaty if the reservation is not adopted.

The Panamanian government is reportedly split over its indications of opposition to the DeConcini reservation.

Washington Post special correspondent Marlise Simons reported from Panama City on Friday that officials were insisting they had no intention of rejecting the treaty just because of the DeConcini reservation.

Senate Majority Leader Robert C. Byrd (D-W. Va.) said at his regular Saturday press conference that the Senate should ignore the controversy in Panama and "just continue with our hands on the plow" to consider the second treaty.

"We're seeing a venting of some pressures, pressures against the government there," Byrd said. "And it behooves us to keep our eye on the ball, and to make our decision . . . on the merits of the treaty, and what's in the best interests of the United States."

Byrd said he is still "cautiously optimistic" that the second treaty, the Senate will approve. He said he has had no indication that the Panamanian protects have change any votes.

Carter sought in his press conference to reassure Panama that the DeConcini reservation does not indicate a U.S. intention to intervene in Panama's affairs.

"The DeConcini amendment is not what I would have preferred, but I think it is accurate to point out that the text of the treaties specifically says, in language that Gen. Torrijos and I personally wrote down, that we do not have any intention nor right to interfere in the internal affairs of Panama," he said.