MEXICO CITY (AP) _ Mexico says it will supply financially strapped Nicaragua with 320,000 barrels of oil this year under special purchasing terms.

Agriculture Secretary Eduardo Pesqueira Olea on Thursday announced the agreement after a joint Mexican-Nicaraguan economic commission met this week in Managua, Nicaragua.

The oil will be supplied from July through September, with an additional 410,000 barrels to be provided in the final three months of the year, the government news agency Notimex and the newspaper El Nacional reported. Credit terms for the 410,000 barrels have yet to be negotiated, the reports said.

Nicaragua, wracked by an insurgency against the leftist government, has had difficulty paying its bills, causing Venezuela to cut off oil shipments.

Mexico, too, had turned off the spigot. But a government statement issued earlier in the week said that Mexico sent an emergency shipment of 250,000 barrels of oil in March.

Last week, Nicaraguan President Daniel Ortega said the Soviet Union promised to provide his country with 80 percent to 90 percent of its oil needs this year.

The Reagan administration announced a trade embargo against Nicaragua May 1, expressing concern about the Sandinista government's ties to the Soviet Union.

Mexico and Venezuela, the main oil exporters in Latin America, have been providing oil to eight Central American and Caribbean nations at easy credit terms since 1980 under the San Jose pact.

The pact was renewed last August but credit terms were tightened, a reflection of lower oil prices and smaller revenues to many oil-exporting countries.