DUBAI, UNITED ARAB EMIRATES, SEPT. 28 -- U.S. naval forces discovered what may be a new minefield in the southern Persian Gulf last night and warned merchant shipping today to avoid the area near the entrance to the Strait of Hormuz.

The suspected mines were found a week after U.S. military forces assaulted an Iranian mine-laying vessel, the Iran Ajr, about 200 miles to the north in the gulf.

Meanwhile, the U.S. ambassador to Bahrain, Sam H. Zakhem, told reporters today that the Navy had located and cleared seven of the nine mines the Iran Ajr laid last week in waters north of Qatar before it was attacked by a U.S. helicopter.

The latest mine discovery was madelast night, according to Navy officials, by the USS Kidd, a destroyer. Sources said that the Middle East Force commander, Rear Adm. Harold J. Bernsen, was called out of a dinner in Bahrain for Defense Secretary Caspar W. Weinberger. The sources said Bernsen excused himself from the dinner, saying, "Those damned Iranians have done it again."

Lloyd's of London warned vessels in the lower gulf today "to keep a sharp lookout and navigate with caution" near the mouth of the gulf.

Shipping sources here said a salvage tug that inspected the mined area 15 to 20 miles off Dubai spotted several underwater objects that were believed to be contact mines tethered to the seabed and designed to strike the subsurface hull of passing vessels.

There were conflicting reports of how many suspected mines were found, with some sources reporting three and others five.

Weinberger, on a stopover in Cairo today after leaving the gulf region, met with Egyptian President Hosni Mubarak and Defense Minister Abdel Halim Abu Ghazala.

In remarks after the meeting, Weinberger said it was "apparent that Iran will not agree to a cease-fire" in the seven-year-old war between Iran and Iraq, and he urged the international community to "proceed together on an {arms} embargo resolution" in the United Nations "as soon as we can."

"We wanted to get an arms embargo against Iran, and we think it is vital to try to maintain unity in the U.N. if we can," Weinberger said, "but I think it is quite apparent Iran is not going to agree to a cease-fire."

Weinberger also said he had no knowledge that any of the 26 Iranian seamen captured during the attack on their mine-laying vessel last week and released to Iran over the weekend had asked for political asylum.

"The question never arose," he said, adding, "I don't know where any of that came from."

Zakhem had told reporters in Bahrain on Saturday that he believed some of the Iranians would have wanted to stay in the West had they been given an opportunity to seek asylum.

Also, reports attributed to sailors aboard U.S. warships involved in the attack on the mine layers indicated at least two of the Iranians had sought asylum.

Speaking to reporters today in Bahrain, Zakhem said Bernsen assured him that none of the Iranians had asked for political asylum.

Zakhem also said that American and other western naval forces in the area are coordinating their mine-hunting efforts and that it is "logical to deduce" that the gulf is being divided into areas of mine-sweeping responsibilities.

He said he did not know whether Soviet naval forces in the area were part of the coordination effort.