Kuwait has chartered its first U.S.-owned supertanker with an American crew aboard, a move likely to deepen the Reagan administration's involvement in protecting Kuwaiti oil exports from the threat of Iranian attack in the Persian Gulf.

The Maritime Administration announced yesterday that it has agreed to charter the 264,000-ton Maryland for two years to Delaware-based Chesapeake Shipping Inc., a subsidiary of the Kuwait Oil Tanker Co.

Kuwait will pay $5 million, half of it to cover costs of repairs and inspection, and will operate the vessel in the gulf crude oil trade, the maritime agency said.

The Maryland will operate "under the U.S. flag and {be} fully crewed by U.S. citizens," with Gleneagle Shipping Management of Houston acting as operator for Chesapeake, it added.

It was not clear if Kuwait will charter a second tanker, as it once indicated.

The United States is providing military escorts in the gulf for 11 Kuwaiti tankers that have been re-registered here and now fly the American flag. But the only American on these ships is the captain.

After being repaired and inspected, the Maryland is scheduled to head for the gulf by mid-November.

Sen. Frank H. Murkowski (R-Alaska), who sponsored an amendment last July urging the administration to charter U.S. tankers rather than reflag Kuwaiti ones, hailed the announcement.

"{This} marks the first time that what we'll be protecting in the gulf will be an American ship, flying the American flag and manned by an American crew," he said in a statement.

"This is a good step in the right direction in defining our policy in the Persian Gulf," he added. "Until now we've been providing the American flag and our Navy's protection to ships that really remain Kuwaiti ships -- no matter what kind of legal fiction we engage in regarding reflagging."

The decision to allow Kuwait to charter a U.S. tanker received careful administration review after congressional charges that it had not given sufficient thought to the risks and implications of its reflagging policy.

A congressional source said the decision to approve Kuwait's chartering of U.S. supertankers was taken after the administration found just three readily available. This was seen as reducing the risks of exposing a large number of Americans to possible Iranian attacks.

The Maritime Administration statement said Chesapeake Shipping, one of six companies to bid for purchase or charter of the Maryland, "provided the greatest financial return to the {U.S.} government" by offering $5 million for the two-year period. All operating costs will be paid by Chesapeake.

Another company, Petrofina, which also has one supertanker available, had complained earlier that the Maritime Administration and Kuwait had already reached an understanding, putting the U.S. government in the position of competing unfairly against private American firms.