52 Americans Leave Iraq; U.N. to Mediate : Gulf crisis: Women and children from the embassy arrive in Turkey. More Westerners are rounded up. The secretary general is to meet with Baghdad’s foreign minister.

WASHINGTON — The government of Iraq permitted a convoy of 52 women and children from the U.S. Embassy in Kuwait to flee Baghdad for freedom Sunday, but three young males in the group were turned back at the Turkish border, and President Saddam Hussein ordered the roundup of more Westerners in Kuwait.

The American youths denied exit by Iraqi soldiers at the frontier were expected to return to Baghdad to join male diplomats still being held hostage there. Meanwhile, at least two more Americans and eight British subjects were taken into captivity in Kuwait, and Iraqi forces maintained their siege on holdout diplomats at Western embassies there as part of what a top Iraqi official described as a defensive bid “to avoid war.”

There were signals, however, of a new desire to blunt the crisis. The United Nations announced that Secretary General Javier Perez de Cuellar will travel to the Middle East to seek a way out in a meeting with Iraqi Foreign Minister Tarik Aziz. And both U.S. and Iraqi officials muted past rhetoric and expressed hopes for resolution short of military conflict.

“We just now have our strategy in place,” said Brent Scowcroft, the White House national security adviser. “I think it’s time now to see whether or not it will work, and that’s what we’re prepared to do.”

Despite new U.N. authorization to use force, American and British warships held their fire as they stalked sanctions-evading Iraqi oil tankers in the Persian Gulf region. A spokesman in Baghdad warned that Iraq would “sink ships” in response to an attack.

The planned session between the U.N. chief and Iraqi officials represents the first formal attempt by the world body to mediate the 25-day-old crisis and comes in the wake of repeated condemnations of Iraqi actions by the U.N. Security Council.

Both U.S. and Iraqi officials expressed support for the meeting, scheduled for Thursday in Jordan. A spokeswoman for the secretary general said Perez de Cuellar and Aziz will “engage in a full exchange of views on the crisis.”

But British Prime Minister Margaret Thatcher bluntly warned that a diplomatic end to the confrontation is “most unlikely.” And as military forces from a dozen nations continued to mass across the border from Iraq, the Pentagon’s U.S. Central Command moved its headquarters to Saudi Arabia.

The State Department declined to identify the three young males, apparently teen-agers, who were prevented from crossing into Turkey with other dependents of U.S. Embassy personnel in an apparent violation of Iraq’s promise of safe passage. A 13-car convoy carrying the 55 dependents left Baghdad before dawn for what is normally an eight-hour mountainous journey to the Turkish border town of Habur. But the trip became a 22-hour ordeal punctuated by a lengthy dispute at the frontier.

Officials from the American Embassy in Baghdad accompanied the convoy, and the young American males remained in their custody after being separated from the women and other children.

The 52 women and children permitted to leave Iraq were met at the border by officials from the American Embassy in Ankara and escorted by bus to the southern Turkish city of Kiyarkbakir, a State Department official said. They were expected to fly back to the United States today.

About 54 male American diplomats who had fled Kuwait last week under similar guarantees of safety remained confined to the U.S. diplomatic compound in Baghdad. Iraq’s ambassador to the United States, Mohammed Mashat, said in a television interview Sunday that Iraq had decided to hold the officials hostage “because we want to avoid war.”

Iraqi Foreign Minister Aziz explained in a CNN interview that Iraq feels threatened, adding, “If they (the hostages) will prevent American genocide against us, then they will serve a noble purpose.”

The drama over captive diplomats came as Iraqi forces in Kuwait city launched new efforts to take other Westerners from their homes in what appeared to be a widening strategy to guard against attack by Western forces.

State Department spokeswoman Anita Stockman said two additional Americans were taken into custody early Sunday in Kuwait city by Iraqi troops, making a total of at least 58 U.S. citizens rounded up in the war zone and transferred to undisclosed locations.

Britain’s Foreign Office said Sunday that eight more Britons had been removed from their homes and transferred to an undisclosed civilian establishment. An estimated 147 British subjects are now in Iraqi custody. At the same time, eight Frenchmen were moved from their homes to the Regency Hotel in Kuwait city, where dozens of their countrymen are being detained.

Iraq’s Hussein has said the foreigners will be held at key military and economic sites as human shields against military action, and reports from workers fleeing Iraq have placed one group of Americans at an Iraqi chemical plant.

The roundup in Kuwait followed the effective isolation by Iraqi forces of foreign embassies there, which remain surrounded by Iraqi troops who have shut off power and water supplies and blocked traffic in and out of the compounds.

State Department officials said Sunday that U.S. Ambassador W. Nathaniel Howell and an estimated nine other Americans left behind at the embassy remain in good spirits and are well-equipped to weather a prolonged standoff.

After speaking by telephone to the ambassador, John Kelly, assistant secretary of state for Middle Eastern affairs, reported that the diplomats are “isolated and sealed off from the rest of Kuwait and, thus, very hampered in helping out the American citizens there.”

But he added in an interview televised on CBS: “They’re holding fast and doing fine.”

A senior White House official reported separately that Iraqi forces had entered the Chinese Embassy in Kuwait in what would be the first such breach of a diplomatic compound there. But the State Department said it had no independent confirmation of the incident.

In the parallel standoff at sea, two dozen American vessels continued to shadow nine Iraqi tankers carrying shipments of oil in the Persian Gulf region in an apparent attempt to defy the sweeping U.N. trade embargo imposed more than two weeks ago.

Despite new U.N. authority to use “commensurate measures” to enforce the sanctions, the U.S. and other Western naval vessels refrained for the second straight day from using force to halt the ships, some of which have ignored previous warning shots.

For the first time Sunday, Iraq’s information minister, Latif Jasim, warned that his country’s forces are prepared to retaliate if fired upon. “We will sink one of their ships, maybe two,” he said, “and if they attack us, we’ll attack them.”

But Scowcroft, Bush’s national security adviser, promised amnesty to Iraqi ship captains who request it and suggested that their defiance so far was a product of Hussein’s reported threats to hang anyone who permits his ship to be boarded.

And Pentagon officials played down the new Iraqi threat, saying it had played little part in their calculations. With the Iraqi oil vessels steering clear of foreign ports, one source said, “There has been no opportunity for any type of interdiction.”

Another military official said that U.S. naval vessels on the lookout for Iraq-bound shipments headed through the Jordanian port of Aqaba have now stopped and boarded more than a dozen foreign-flagged vessels in the Red Sea. None was found to be violating the sanctions, the official said.

The international fleet now patrolling waters near Iraq to enforce the sanctions includes vessels from Britain and France as well as the United States. But the Soviet Union, despite voting Saturday for the Security Council resolution that authorized force in the blockade, made clear Sunday that its vessels would play no part in such action.

The maneuvering at sea came as the U.S. Central Command and its top officer, Army Gen. H. Norman Schwarzkopf, set up its headquarters for the first time in Saudi Arabia, where it will coordinate a rapidly growing U.S. fighting force.

In a separate action, the Army on Sunday ordered 50 more Army reserve and National Guard units in 25 states to report for active duty by Aug. 31 as part of a move that is ultimately expected to call 40,000 citizen soldiers to active duty.

Reports from Saudi Arabia, however, indicated that commanders at several U.S. base camps are still lacking vital equipment, including ground-based anti-aircraft systems to protect American forces. There were also isolated reports of shortages in spare parts.