After years as a wallflower, the United Nations shows signs of becoming the late-blooming belle of the diplomatic ball.

Renewed interest in the 43-year-old organization stems from the success of Secretary General Javier Perez de Cuellar in cajoling Iran and Iraq into a cease-fire, soon after the U.N. brokered an agreement for the withdrawal of Soviet troops from Afghanistan.This has raised hopes for success with such knotty problems as Namibia, Western Sahara, Cyprus and Cambodia.

But the United Nations ironically is in the spotlight at a time when it is down at the heel and starved for affection - and cash - from the United States, once an ardent beau.

Despite a financial crunch that officials say could close the organization by November, it has launched an ambitious peacekeeping operation to monitor the cease-fire in the Persian Gulf.

At a time when defaulting members, led by the United States, are more than $600 million in arrears, it is sending 350 military observers and nearly 1,100 support staff to the Iran-Iraq warfront.The cost for the first six months is put at $74 million.

The U.N. Iran-Iraq Military Observer Group is only the latest addition to field operations that have sent thousands of blue-helmeted peacekeepers to Cyprus, southern Lebanon, the Golan Heights and other trouble spots.

No one yet knows if the fresh focus on the United Nations and its low-key but dogged Secretary General signals a new lease on life after years on the sidelines.

Sir Brian Urquhart, a former Undersecretary General, attributes its renewed prominence mainly to "an outburst of common sense" coupled with an easing of East-West tensions.

In conflicts such as the Persian Gulf war, where the superpowers are not directly involved, Urquhart believes sheer exhaustion sometimes affords the United Nations an opening.

In such cases it is easier to "say you are cooperating with the secretary general and the Security Council than it is it to say you were beaten on the battlefield," he said.

The United Nations received a boost last September when Soviet leader Mikhail Gorbachev signaled hopes for revival.

In the Soviet press he wrote that a proposed comprehensive security system would "become operative to the extent that the United Nations, its Security Council and other international institutions and mechanisms function effectively."

Despite a spate of U.N. reforms and a noticeable drop in anti-American rhetoric, the United States has not reinstated its full contribution, citing its own budget tightening and lingering dissatisfaction with the world body's operations.

This leaves Secretary of State George Shultz and the chief American U.N. envoy ambassador Vernon Walters in the awkward position of praising the U.N.'s peacemaking efforts and reform attempts while failing to come up with the needed cash.