Senate leaders met again yesterday with Sen. Dennis DeConcini (D-Ariz.) to try to agree on language for a new understanding to the second Panama Canal treaty that might make it acceptable to both Panama and a two-thirds majority of the Senate.

The meeting ended inconclusively. DeConcini said afterward that he believed the Senate leaders, including Majority Leader Robert C. Byrd (D-W.Va.), "know where I'm coming from."

An aide to one of the senators present said those involved remained hopeful that a compromise could be worked out by the beginning of next week. The Senate is scheduled to vote on the treaty Tuesday.

The closed-door discussion centered on the possibility of another reservation, drafted by the leaders, which would declare that nothing in the treaties would be interpreted as giving the United States a right to intervene in the internal affairs of Panama.

The wording, its authors hoped, would not be seen by DeConcini as conflicting with his own, earlier reservation allowing U.S. intervention to keep the canal open against any kind of internal threat.

Panamanian officials are angry over the Deconcini provision, calling it an insult to their country's sovereignty and hinting it might force them to reject the treaties entirely.

Senate leaders are trying to hold their own shaky coalition of treaty supporters together for the show down vote on Tuesday.

The first of the two treaties, providing for the canal's neutrality after the year 2000, was approved a month ago by a 68-to-32 vote - one more than the required two-thirds majority.

The second pact spells out procedures for the United States to turn the historic waterway over to Panama by that date.

Sen. S. I. Hayakawa (R-Calif.) called a press conference yesterday to make threatening noises about withdrawing his support for the treaties, but he refused to be specific.

Hayakawa released a letter he has sent to President Carter expressing dismay at the administration's foreign policy, which he characterized as "silence or timid acquiescence in the face of determinded communist aggression." The letter suggested that unless he got some assurance from Carter of firmness he might vote no on Tuesday.

But reporters at the press conference - many visibly angry at what appeared to be a publicity stunt - could not get Hayakawa to say what he was demanding, or whether he really would vote against the second treaty after supporting the first.