Paramarian leader Omar Torrijos promised sweeping improvements in his country's human rights situation yesterday and made a conditional offer to step down from power if that would ease ratification of the canal treaties by the U.S. Senate.

Torrijos made the promises to six U.S. senators who had arrived in Panama four days earlier uncommitted on the treaties. Four of them thereupon indicated that they will support the pacts.

Torrijos promised to permit the return of 60 political exiles, easing of press censorship and an end to martial law provisions permitting detention without trial.

"If the Senate were to say that for the ratification of the treaty they needed that I go. Iwould leave, "the Associated Press quoted Torrijos as saying in an impromptu meeting with the six senators before their morning departure.

He later qualified this, indicating--as he had in lengthy talks with the senators earlier--that he might seek election to the presidency after the canal pacts are ratified.

"If 51 per cent of the people support me, I stay," he said. Torrijos seized power in a coup in 1969.

Sens. Howard Metzenbaum (D-Hawali)said they would now offer unqualified support for the pacts. Matsunaga said he would lobby for them.

Sens. Don Riegle (D-Mich) and Walter Huddleston (D-Ky.) said they cauld support the pacts if Torriijos carries out his promises on human rights. Senate majority Leader Robert Byrd (W.Va.) and Sen. pual Sarbanes (D.Md.) said they would still reserve judgment.

Sen. James Sasser (D-Tenn.) had already left Panama for home when Torrijos made his declarations on human rights.

The delegation of Democrats, all of whom support the Carter administration on most issues, is considered a bellwether of the President's chances for approval of the pacts, which would turn control of the canal over to panama by the year 2000.

Torrijos, explaining his vow to end arbitrary imprisonment, said, "The senators . . . very decently, very properly made this observation"--that holding prisoners without trial is "not right."

Several months ago Torrijos offered to open the jails to human rights groups and to free any political prisoners they might find.

His promise yesterday to allow return of remaining political exfles may have the strongest impact in Washington, where serveral exile Panamanian rightists have been lobbying against ratification of the treaties.

In an earlier concession to critics from abroad, Torrijos added yesterday that he will use $50 million in promised U.S. aid for humanitarian rather than mulitary purposes.

Byrd, while witholding his own commitment to the treaties, said of Torrijos's promises: "It was a positive step. I don't see but that it can help but improbe the atmosphere for ratification."

During the senators' four-day stay, Torrijos actel as guide in an often colorful crisscrossing of the isthmus, from Indian villages to his own seaside home.

President Carter, asked in Annapolis yesterday about Torrijos's offer to resign, told reporters: "I don't consider General Torrijos to be an obstacle."