U.S. officials say Saudi Arabia has offered to help Kuwait search for antiship mines Iran is suspected of placing in the northern Persian Gulf to complicate the U.S. plan to provide a military escort for Kuwaiti tankers.

In a related development, the U.S. Navy has accelerated its preparations for sending the battleship USS Missouri and three accompanying warships to the Persian Gulf next month if President Reagan should decide to deploy that much extra firepower there.

No final decision has been made on whether to send the Missouri, Navy officials said last night, but preparations are being made so the president has the option available. The armor on the World War II battleships, advocates say, is thick enough to withstand most of the weaponry Iran could bring to bear if it tried to interfere with U.S. escort operations in the gulf.

But some defense officials argue that sending in a battleship would be overkill and would intensify anti-American feelings in the Middle East. The Pentagon plan that has been approved calls for having nine U.S. warships in the gulf, three more than the present force, to escort 11 Kuwaiti tankers flying the American flag.

The Saudis have four minesweepers purchased from the United States that could be used in the operation in the northern gulf, the officials said.

The United States has no minesweepers assigned to the six-ship Middle East Force based in the gulf, but it does have helicopters that could be used to clear mines. The force is being expanded to nine ships to meet the demands for escorting 11 Kuwaiti oil tankers being placed under American flags for protection from possible Iranian attacks.

The Saudi offer to use its tiny navy to help search for mines represents a further Saudi commitment to the U.S. protection plan.

Last week, the Saudis also informed the United States that they will use their five newly arrived Airborne Warning and Control System (AWACS) aircraft in the lower gulf to provide surveillance and intelligence information about possible Iranian attacks on the reflagged Kuwaiti tankers and their U.S. naval escorts. The Pentagon has sent a team to the gulf to assess the potential danger of mines. Since the Iraqi attack on the USS Stark May 17, four ships have struck mines, primarily in the channel leading into Kuwait's main oil port at Mina al-Ahmadi.

A senior administration official said last week that the mines apparently were being placed deliberately by Iran, which has been threatening Kuwait because of its strong financial and diplomatic support for Iraq in its war with Iran.

Iran is believed to have placed most of the mines in Kuwaiti waters the U.S. escort warships are not scheduled to enter. But one Soviet tanker chartered to Kuwait has hit a mine outside Kuwaiti waters.

Rep. Les Aspin (D-Wis.), chairman of the House Armed Services Committee, warned yesterday that the mines raised the prospect that the United States "will safely escort a {Kuwaiti} ship for 600 miles, wave it goodbye, turn around and sail off, only to hear a loud boom behind us."

"We would look rather silly," Aspin said.