Prospects for talks aimed at defusing the crisis in Central America appear to be growing.
Much of the impetus comes from a new willingness on the part of both Cuba and the United States to reassess their diplomatic options in an area that has increasingly taken on critical international significance.
However, in commenting on a peace plan introduced by Mexico, US Secretary of State Alexander M. Haig Jr. said Monday that the United States would negotiate on its own behalf, and not through Mexico.
Mexican Foreign Minister Jorge Casteneda de la Rosa plans to visit Cuba and Nicaragua within the next 10 days in an effort to bridge the gap between the United States and those two governments. This could prove, say Mexican sources, a forerunner to direct Washington-Havana and Washington-Managua talks.
Whether or not the United States is willing to directly talk with Cuba still remains unclear. Although Secretary Haig insisted that the Soviet Union, Cuba, and Nicaragua were involved in the ''command and control'' of military operations in El Salvador, he said:
''That does not mean--I repeat, that does not mean nor did it ever mean--that the Soviets or the Cubans for that matter must be invited to the negotiating table.''
Secretary Haig gave details for the first time of US proposals presented to Nicaragua last year and to the Mexicans Monday that would provide US assurances about ''nonaggression'' against Nicaragua provided its goverment withdrew support for Salvadoran guerrillas.
Mexican sources have noted fresh signs that both Cuban President Fidel Castro and Nicaragua's top leadership want talks with the US on Central America and other issues. Although largely ignored in recent months by Washington, Dr. Castro has been angling for such talks with the Reagan administration. State Department spokesmen now indicate the door to these talks may be open.
The attitude of the US to Mexican peace moves has also changed considerably this past week. For one thing, Washington is under mounting pressure to prove its contention that Nicaragua, along with Cuba and the Soviet Union, are supplying the Salvadoran guerrillas. Evidence presented so far has not won much acceptance by the US public nor by Congress.
Additionally, last week's much ballyhooed presentation of a Nicaraguan guerrilla who had fought in El Salvador was an embarrassment to the Reagan administration. The young guerrilla in a Washington press conference recanted his earlier story about being sent to El Salvador by Nicaragua after training in Cuba and Ethiopia.
Washington, moreover, is beginning to realize that Nicaragua's oft-voiced concern about the security of its borders is not simply rhetoric but represents a deep-seated worry. The US is coming to appreciate that the Nicaraguans are genuinely concerned.
This changing US view is due, at least in part, to the recent 10-day visit to Washington of Jaime Wheelock Roman, Nicaragua's agriculture minister and one of the top Sandinista commanders.
Mr. Wheelock's two-fold message is that Nicaragua does have legitimate concerns--but that it wants good relations with Washington--was heard.
For the moment, the focus of the peace effort centers on Mr. Casteneda and his travels. He returns first to Mexico City for talks with his President, Jose Lopez Portillo, and other Mexican officials, including presidential candidate Miguel de la Madrid Hurtado. Then next week he goes to Havana and Managua.
For its part the US now is looking at the possibility of giving some sort of nonaggression guarantee to Nicaragua. Secretary Haig, who claims Nicaragua is directing and arming Salvadoran guerrillas, has sought assurances these alleged practices will cease.
But Managua is likely also to want some guarantees that clandestine operations will not be mounted against the Central American country. Press reports that President Reagan had approved a plan to finance mercenary activities against Nicaragua stirred a congressional storm and butressed Nicaraguan claims that its arms buildup is necessary for self-defense.
US officials have been tight-lipped about reported plans, but the suggestion that such activities might take place was received with concern in Nicaragua.
Mexico is pushing a number of countries--in Central America and South America , in addition to the US--for nonaggression guarantees. The issue is important because Nicaragua justifies its current arms buildup on its fear of attacks by neighbors.