With cease-fire negotiations between the contras and the Sandinista government of Nicaragua a possibility, the United States has accelerated shipments of military supplies to the rebels, enabling them to fight well into next year, administration and congressional sources say.

Last month, according to a State Department official, almost twice as many military and logistical supplies were parachuted to rebels inside Nicaragua than in each of the previous three months. Most deliveries were made by the Central Intelligence Agency from flights originating in Honduras, officials said.

"{The contras} have more supplies than they've ever had before," the State Department source said.

Congressional experts said the supplies were paid for out of the $100 million contra aid package for 1986, which included $70 million in military assistance. They said deliveries did not resume until December, more than a month after contra aid received final passage.

"They obligated all the money, but it's taken this long to get it all delivered," said one House source.

The increase is partly due to increased fighting, said an official who spoke on the condition that he not be named. But he added, "They are preparing the battlefields. They are preparing for their future operations."

Bosco Matamoros, military spokesman for the contras, said the rebels are burying the equipment in their areas of operation enabling them to fight even if U.S. military air drops cease.

The Central America peace plan signed last August called for a regional cease-fire to be in place by Nov. 5 and all outside aid to insurgents, such as the contras, to stop at the same time. But indirect cease-fire talks between the Sandinistas and the contras are just beginning, and Honduras has only recently pledged to cut off support for the contras.

"I believe the administration is trying to get as much military materiel out there as they can to improve the performance in the field and to have a strong position at the negotiating table," said a Central American diplomat closely involved in the peace talks.

The supplies also could allow the contras to keep fighting even if Congress balks at approving future military aid, officials said.

Reagan last month delayed a request for $270 million more for the contras, mostly in military aid, until all Central American leaders assess the progress of the peace pact in early January.