Secretary of State George P. Shultz, saying the United States wants to give peace in Central America every chance, promised yesterday that the Reagan administration will wait "until next year" before asking Congress for $270 million in new military aid for the Nicaraguan contras.

"I can tell you that we will seek no further military aid for the resistance until next year," Shultz told foreign ministers of the 31-member Organization of American States gathered here for the annual OAS Assembly.

Nicaraguan President Daniel Ortega arrived here last night and is scheduled to address the assembly this morning. On Monday, Shultz left open the possibility of a meeting with Ortega, but the State Department yesterday ruled that out.

In confirming unofficial reports that the administration had decided to defer its aid request until January or later, Shultz tacitly acknowledged that Congress will not vote for new contra aid at this time. Instead, the Democratic-controlled House and Senate want a clearer picture of whether the five-nation Central America peace agreement is working.

As a result, the administration, in a shift of tactics, has eased its former unrelenting hostility toward Nicaragua's Marxist Sandinista government and has adopted a more flexible carrot-and-stick approach toward Managua. On Monday, President Reagan offered to resume high-level U.S. talks with Nicaragua if the Sandinistas hold indirect talks with the contras through that country's Roman Catholic primate, Cardinal Miguel Obando y Bravo.

In following up yesterday with the pledge to delay the contra aid request, Shultz responded to pleas from the four other presidents who signed the peace accord in Guatemala last Aug. 7. They have called for a halt in outside aid to insurgent forces until January, when an assessment is to be made of how well the agreement is working.

But Shultz also warned that the administration has no intention of abandoning the contras. He said:

"This does not mean that we will sit idly on the sidelines if the Sandinistas try to strike for a military victory. We will not abandon the resistance fighters to face advanced Soviet weaponry and Cuban advisers with their resources exhausted. We will not permit the peace process to become a shield for the physical elimination of the Nicaraguan resistance. It does mean we will give peace every chance."

He also said the administration eventually will seek new contra aid, but he added that "the specific forms will depend on what happens in the implementation of the Guatemala agreement. If it works as we all hope, it will be directed to the peaceful reintegration of the resistance into a free Nicaragua; if it does not, it will be used to enable the struggle for freedom to continue until it does succeed."

The Sandinistas so far have not responded to the latest U.S. approach, and Ortega may give his government's reaction today. On Monday, Shultz hinted that some moves this week by the Sandinistas toward greater freedom of the press, freedom for political prisoners and dialogue with the contras could result in his meeting with Ortega.

Yesterday, however, State Department spokesman Charles E. Redman slammed the door on that possibility. Redman said:

"What the president and the secretary made clear {Monday} was that the kind of talks we're contemplating are regional ones that would involve all the Central American countries, and these talks would take place only after serious talks between the Sandinista regime and the Nicaraguan resistance are under way. Clearly, there is no possibility for that to happen this week."

Adolfo Calero, one of the six members of the contra movement's political directorate, told editors and reporters of The Washington Post yesterday that the contras had been consulted in advance about Reagan's tentative offer of talks with the Sandinistas. He said:

"We expressed our acceptance of the need for this country to talk with the Sandinistas. However, we observed that it had to be in the context of a regional approach. There is no sense for the United States to refrain from such talks in this regional context. We knew it was going to happen."

In the meantime, a delegation of U.S. senators who made a weekend trip to the region disagreed about the attitudes they encountered in talks with leaders of Nicaragua, El Salvador, Honduras and Costa Rica. The group did not visit Guatemala, the fifth country in the agreement.

Sen. Christopher J. Dodd (D-Conn.), who led the delegation, said, "Every single one of the heads of state believed the process was working." But Sen. John S. McCain (R-Ariz.) said Republicans in the group were disappointed by Nicaragua's lack of compliance, and Sen. Steve Symms (R-Idaho) added: "Some of my liberal colleagues look for every sign of evidence that something good is happening."