SHARJAH, UNITED ARAB EMIRATES, JUNE 19 -- Troops supporting coup leader Sheik Abdulaziz bin Mohammed Qassimi dug into sandbagged positions in this Persian Gulf port today, and diplomats said the United Arab Emirates' political crisis was unlikely to be resolved soon.

The UAE, a confederation of seven sheikdoms, including Sharjah, has been split by the palace coup that Abdulaziz staged Wednesday against his brother, Sheik Sultan, while the ruler was in London.

{The sheikdom of Dubai, one of the most powerful in the UAE, has threatened to intervene on behalf of Sharjah's ousted ruler, but Abdulaziz warned Friday that he would fight with the 3,000 national guardsmen loyal to him, The Associated Press reported.}

The diplomats said another powerful member of the confederation, the oil-rich state of Abu Dhabi, is opposed to using force.

The UAE's Supreme Council, comprising the leaders of the sheikdoms, isssued a bland statement yesterday playing down any idea of conflict among the emirates, but western diplomats said there appears to be no prospect of an easy solution to the crisis, which neighboring nations fear could undermine their own security.

Steel-helmeted national guardsmen backing the rebel strongman dug into sandbagged positions inside the Royal Palace today, military sources said. Soldiers armed with Soviet-made AK47 Kalashnikov assault rifles sheltered themselves from the scorching sun under beach umbrellas erected over sandbagged checkpoints around the palace.

Troops manning heavy machine guns guarded other key installations, including the telephone exchange and main post office, in the tiny strip of sand and modern skyscrapers that is home to 269,000 people. Sharjah International Airport and the state's daily newspaper, Al Khaleej, were closed.

Dubai newspapers today carried photographs of the deposed Sultan meeting loyal relatives and supporters in Dubai, where he is awaiting developments under heavy protection. His wife quoted him as saying he wants to resume his rule.

But Abdulaziz, at a meeting with a delegation from the UAE Supreme Council yesterday, flatly refused to call off the coup.

In addition to the national guard, which he commanded before the takeover, Abdulaziz is chairman of the UAE federation of chambers of commerce and has widespread support from the emirate's business community, which accuses Sultan of ruining the economy.

Sultan's government has raised discontent with a series of unpopular economic policies. In October 1985, the government prohibited the sale of alcohol in public places, dealing a severe blow to the burgeoning tourist trade.

Arab diplomatic sources in Abu Dhabi said the coup was prompted by a financial crisis. Bankers estimated Sharjah's debts at around $400 million.

Sharjah is the third largest of the seven sheikdoms that form the nation, a member of the Organization of Petroleum Exporting Countries that was established after independence from Britain in December 1971. The others are Abu Dhabi, Dubai, Ras al Khaimah, Fujaira, Ajman and Umm al Quiwain. Sultan has ruled Sharjah since 1972.

Buoyed by a major oil and gas find in 1980, Sharjah embarked on an ambitious development plan. But the dramatic fall in world oil prices in 1986 plunged Sharjah into a financial crisis and forced it to borrow heavily from local and foreign banks.