The Senate Republican leadership which will be a key element in ay fight over ratification of new Panama Canal agreemeents, acceded to President Carter's request yesterday to reserve judgment on the substance of the new negotiated treaties.

Senate Minority Leader Howard H. Baker of Tennessee and Minority Whip Ted Stevens of Alaska said they would not comment on the treaties until they had studied them.

But Stevens and others, including Majority Leader Robert Byrd of West Virginia, predicted atough battle in gaining ratification of the treaties, which would give Panama control of the canal and of the Canal Zone by the year 2,0000.

This would be particularly true if most of the Senate's 38 Republicans lined up against ratification, thus magnifying the importance of the Republican leadership. Ratification will require 67 votes, two-thirds of the Senate.

The President met for 90 minutes yesterday with the two American negotiators of the treaties, Ellsworth Bunker and Sol Linowitz, to discuss details of the agreements, which are still not in final form.

White House press secretary Jody Powell said Carter plans to devote much of to day to reviewing the treaties and hopes to be able to make them public by the end of the day.

Yesterday's meeting was also attended by Defense Secretary Harold Brown, Deputy Secretary of State Warren Christopher and the Joint Chiefs of Staff. Powell said Bunker and Linowitz were "questioned closely" about the meaning of language in the treaties and that Carter reacted "very positively" to the substance of the documents.

The Carter administration has set ratification of the treaties as one of its highes priorities. But Powell said no firm decision has been made on whether to push for a vote this year or wait until next.

Byrd wants the Senate to adjourn by October, leaving little time for action this year. A delay until next year, however, could embroil the issue in the off-year elections, possibly jeopardizing its chances.

"I think they (the administration) know they have a selling job to do," one Senate source said.

In West Virginia, Byrd said ratification faces "an uphill road" in the Senate. He said Carter should take the issue "to the country" to gain popular support before a vote, and that he recently suggested to the President that he enlist former President Ford in such a venture.

Ford's support of negotiations for a new canal treaty cost him heavily in his primary campaign against Ronald Reagan last year, and his strong public support for the treaty could reopen the wounds left from that bruising battle. Powell said Carter has kept Ford informed on the negotiations, having spoken to him as recently as a few days ago, and would welcome his support for ratification.

The former President, vacationing in Vail, Colo., could not be reached for comment. But Reagan issued a statement saying he saw no reason to alter his opposition to turning over control of the canal to Panama, and a Reagan associate said:

"If Jerry Ford wants to go out and make this an issue, he'll lose on it in the Republican Party."

Minority Whip Stevens said that although his initial reaction was to oppose the treaties, he wanted to study them first. He said he had not discussed the matter with Baker and did not know "if a Republican consensus is possible or not" on the issue.

Sen. James A. McClure (R-Idaho) said he and Sen. Jesse T. Helms (R-N.C.) "are preparing legal actions immediately to prevent the administration from taking any further steps to implement this treatey prior to congressional action." Sen. Strom Thurmond (R-S.C.) reportedly will join in that move.

Earlier this year McClure, Helms. Thurmond and three House members made an unsuccessful attempt, which they carried to the Supreme Court to block the treaty negotiations. The courts ruled that challenge premature.

One central issue in dispute is whether Congress as a whole as distinct from the President and the Senate in their treaty-making capacity, has the right to transfer U.S. property. In testimony last month. State Department legal adviser Herbert J. Hansell maintained that the President and the Senate "have concurrent power with the Congress to transfer property belonging to the United States."

Officials yesterday reiterated, as Hansell testified, that the House will have "a major role" in news arrangements for the canal, but they said the precise legislation is still under study.

Administration officials yesterday clarified some confusion over what will be presented to the Senate.There will be two treaties between the United States and Panama, they said, one of them the basic accord effective until the year 2000, and the other a canal "neutrality" pact, with a protocol open for the signatures of other nations.

The latter treaty, and protocol deals with the sensitive question of assured U.S. access to the waterway after the Canal Zone has been fully transferred to Panama by the year 2,000.

Under theis second treaty for what is called a permanent regime of neutrality for the canal, access to it is pledged to all nations, but with a special right of "expeditions passage" for American and Panamanian vessels. This is designed especially to assure uninterrupted passage of American warships administration sources said.

Administration officials also amplified the complex economic arrangements with panama.

As previously disclosed, the United States will pay Panama between $40 million and $50 million a year until the year 2,000 from increased canal toll revenues, plus an additional $10 million to $20 million a year from the canal's operating funds.

The source of this additional payment, officials said, is interest on the capital fund of over $600 million for the Panam Canal Zone, which is on deposit in the U.S. Treasury.

In addition, the United States has agreed to ask Congress for $50 million in military credits and grants to Panama over the next 10 years and to provide Panama with $295 million in credits from the Export-Import Bank, $75 million from the Housing Investment Guarantee Fund and $20 million from the Overseas Private Investment Corp.