U.S. tanks and armored vehicles bucked across a dusty Honduran plain three miles from the Nicaraguan border today in the latest of a series of exercises demonstrating the U.S. military's readiness and resolve in Central America.

The mock assault on a Honduran Army position by 10 M60A3 battle tanks and five M113 armored personnel carriers of the Texas National Guard marked the first use of U.S. armor in joint military maneuvers that have been held here almost continuously over the last two years. U.S. officials call the war games a signal to the neighboring Sandinista government.

In another gesture highly visible to the Popular Sandinista Army on the other side of the border, Honduran warplanes dived and wheeled in practice bombing runs over the advancing armored forces, which U.S. military spokesmen said were simulating a Sandinista attack on Honduras.

No bombs were dropped and no live ammunition was fired in the maneuvers, which are the culminating phase of Big Pine III exercises that began Feb. 11 and are to end May 3.

Following the lead of declarations by President Reagan last week, U.S. military spokesmen sought to portray the maneuvers as strictly a training exercise.

"It is not meant to say anything to Nicaragua," said Maj. William Lowe, an Army spokesman here. "The purpose of this exercise is to train U.S. soldiers. From the Honduran perspective, the purpose is to train Honduran soldiers."

U.S. diplomats here and in Nicaragua have long described the series of military exercises as a show of resolve aimed at the Sandinista leadership in Managua. That also is the spirit in which they have been received by officials in Nicaragua, who also have charged that anti-Sandinista rebels have benefited from U.S. military equipment and construction remaining behind.

A briefing document issued by the U.S. Embassy in Tegucigalpa last April qualified the Big Pine II maneuvers that had been under way then in the same manner.

"This latest series of exercises, and the accompanying naval maneuvers off both coasts of the isthmus, were conducted to demonstrate U.S. resolve and willingness to support our regional friends," it declared. "In addition to the training benefits for U.S. forces, Big Pine II had the political effect of reducing the anxiety felt by Honduras because of tension on the border with Nicaragua."

U.S. and Honduran officials have expressed fears in recent weeks that the border tension could rise again because of an influx of anti-Sandinista rebel forces to their rear camps on Honduran soil. With supplies and money running short, up to 6,000 rebel troops have filtered back across the border to their havens here in the last two months.

Today's exercises took place well west of the main rebel camps, however, on a dry coastal plain leading from the Gulf of Fonseca across Choluteca province, some 80 miles south of Tegucigalpa. The 400-man Texas National Guard contingent has been bivouacked here for some time preparing for its part in the maneuvers. Inevitably, its campsite has been baptized "the Alamo."

Gov. Mark White of Texas -- who is an ex-member of the state guard and by virtue of his office is now its commander-in-chief -- visited his constituents here yesterday, treating them to a down-home barbecue.

A Texas Air National Guard C130 transport plane brought in 43,000 tortillas, 100 pounds of pinto beans and 400 pounds of barbecued meat, according to a U.S. Embassy employe.

The unit has brought to Honduras 17 M60A3 tanks and an equal number of M113 armored personnel carriers. But the small number took part in today's mock attack, along with a tracked trench spanner, according to Lowe.

They sped from the Alamo campsite across the bumpy terrain to a hill defended by Honduran Army soldiers, behind a tank trap dug by U.S. engineers during previous exercises.

According to U.S. Army Lt. Col. Agustin Gomez, the U.S. armor advanced using "Soviet-style" tactics, which he described as straightforward mass advance with little room for on-the-spot decisions by individual tank commanders.

"The reason is to expose them the Honduran defenders to Communist Bloc tactics, to Russian tactics, to Sandinista tactics," he said.

The Reagan administration has warned that Nicaragua's neighbors face a danger from the Sandinistas' growing military arsenal, which includes more than 100 T54 and T55 medium tanks and about 20 PT76 light amphibious tanks, along with a variety of other Soviet-designed weapons.

To further underline what they depict as a threat, U.S. officials shipped to Honduras for display during the maneuvers a pair of the medium tanks, a PT76 tank and two BTR armored personnel carriers, a model also in the Sandinista equipment park.

The three-month Big Pine III exercise will bring a total of 5,000 U.S. military personnel to Honduras, in addition to the approximately 1,200 stationed here permanently between exercises in Task Force Bravo, Lowe said.

The maximum number of U.S. military in Honduras for the exercises at any one time will be 2,300, he added, and a simultaneous naval exercise has been set for the last three weeks of April.