Caught between the Pentagon and a large group of Democratic voters, President Clinton has intervened in a dispute over the Navy's use of a firing range in Puerto Rico, telephoning the island's governor three times in the past five days while also pressing the Navy to compromise.

Because of the timetable for aircraft carriers rotating through the Persian Gulf, by the end of this week Clinton may have to choose between sending Navy ships into a potential combat zone without full training or risking an armed confrontation between federal officers and anti-Navy protesters on the Puerto Rican island of Vieques.

The political alternatives are no more savory. Unless he can quickly engineer a compromise, Clinton will either damage his wife's chances of winning the Senate race in New York, where Puerto Rican voters can swing a close election, or invite Republican charges that his administration compromised national security for political reasons.

At the heart of the dispute is a demand by Puerto Rican residents and political leaders that the Navy halt any further use of its 12,000-acre firing range on Vieques, which has been a key training ground for the ships and aircraft of the Atlantic Fleet since World War II.

The Navy operations have been the target of periodic protests and legal actions since the 1960s. But the current controversy erupted after a civilian security guard was killed by an errant bomb in April. Since then, Puerto Rican leaders across the political spectrum have rallied behind the demand that "not one more shot" be fired at Vieques. Protesters, sometimes numbering in the hundreds, have set up tents on the firing range and vowed that the government will have to force them out if it wants to bomb Vieques again.

In a report last month, a presidential panel concluded the Navy acted insensitively in Puerto Rico by failing to fulfill promises to promote economic development for the 9,300 inhabitants of Vieques and to limit the use of live ammunition. However, the panel, chaired by Deputy Assistant Defense Secretary Frank Rush, also backed the Navy's claim that live-fire exercises at Vieques are "vital" to preparing forces for combat and that "without such training, the risk to personnel is increased."

Clinton has to weigh that risk now, because a carrier battle group led by the USS Dwight D. Eisenhower is due to train at Vieques in early December before departing for the Persian Gulf on Feb. 18. While the carrier's pilots have completed their preparatory training elsewhere, three surface ships would have to sail without meeting the Navy's standard qualifications unless they can practice firing their guns at shore targets with live ammunition, according to a senior Pentagon official.

Vieques is the only place that the Atlantic Fleet conducts such exercises. The Pacific Fleet uses an uninhabited island off the coast of California.

Clinton first called Gov. Pedro Rossello on Saturday to "make it clear that while he is sympathetic to Puerto Rican concerns, he is also prepared to make tough decisions to ensure the nation's military readiness," said a senior administration official. Clinton suggested that the Navy might agree to forgo the use of live ammunition--limiting itself to "inert" ordnance--and set a date within three to five years to halt all training operations, the official said.

But in the call Saturday and two others since then, including one Monday while the president was visiting Turkey, Rossello refused to budge from his opposition to any further bombing at Vieques.

"Live or non-live, no more bombs, not one more--that remains the governor's position," Alfonso Aguilar, Rossello's press secretary, said yesterday.

The Pentagon, meanwhile, insists that it won't compromise until the Puerto Ricans do.

"A range of options have been examined on our side, including the possible use of inert ordinance, but we can't do anything definitive until the other side shows that it is willing to engage in a meaningful dialogue instead of just restating known positions," said a senior defense official.

If the president decides that the Eisenhower battle group must sail without the training it usually gets at Vieques, the Navy will comply, but not happily. "It has been made clear that a civilian will have to issue an order for those ships to deploy with inadequate qualifications," said a senior military officer.

For the Eisenhower battle group to stay on schedule, Clinton needs to make a final decision by the end of this week, defense officials said. If no long-term solution can be reached, the Pentagon has suggested a one-time deal for the Eisenhower and its escorts to train at Vieques while negotiations continue, but so far Rossello has rejected that proposal.

Clinton's effort to forge a compromise between the Navy and the Puerto Rican leadership is greatly complicated by factors that have nothing to do with Vieques, according to officials on both sides of the dispute.

Some senior military officers openly worry that electoral politics could influence Clinton's calculations, because first lady Hillary Rodham Clinton and Vice President Gore have sided with the Puerto Ricans. "It looks like the deck is stacked against us and against a decision on the merits," said one officer.

Meanwhile, Puerto Rico is mired in a passionate but stalemated debate over whether it should remain a commonwealth--with the benefits of U.S. citizenship but no voting representation in Congress--seek statehood or opt for independence. In this context, Vieques has been one of very few issues to unite residents and politicians of all stripes.

Rossello, the leader of pro-statehood forces, is in a particularly difficult position. If he appears beholden to Washington, he will provide ammunition to his principal opponents, who argue that commonwealth status will best preserve Puerto Rico's autonomy and unique characteristics, such as the use of Spanish as an official language.

CAPTION: Protesters assail Navy training in Puerto Rico during October visit to Philadelphia by President Clinton.