WASHINGTON (AP) _ The Marine Corps has charged a former U.S. Embassy security guard with espionage, alleging he provided to Soviet agents the names and photographs of American intelligence agents attached to the embassy staff in Moscow.

In a formal statement of charges released Friday, the Marine Corps also accused Sgt. Clayton J. Lonetree of providing the Soviets with descriptions of the floor plans and office assignments for U.S. embassies in Moscow and Vienna, Austria.

The charges against the 25-year-old Lonetree include 19 different violations of the Uniform Code of Military Justice. Among the 19 are a single charge of espionage, which under a law passed last year by Congress now carries a maximum penalty of death.

Whether Lonetree will actually be court-martialed on all counts remains unknown.

Under military procedures, the Marine Corps had to file a set of formal charges against Lonetree before the start of an investigative hearing.

That hearing, which will be held before a military lawyer within the next three weeks, amounts to a grand jury hearing in the civil judicial system. The hearing officer and, ultimately, the commanding general at the Quantico Marine Base, will have to decide if there is sufficient evidence to justify proceeding further.

Lonetree was arrested last month and taken to Quantico on Dec. 31, where he has been held ever since.

Pentagon sources have said Lonetree had become sexually involved with a female Soviet agent while working as a guard at the U.S. Embassy in Moscow from September 1985 to March 1986.

The woman worked at the time as a translator on the embassy's staff. Lonetree was later transferred to guard duties at the U.S. Embassy in Vienna, where he ultimately admitted his activities to military authorities in mid- December and was taken into custody.

The charges allege that Lonetree had scheduled meetings with a Soviet agent in Vienna just before his arrest and that the agent was observed appearing for the meetings.

According to the specification of charges, Lonetree kept contact with three different KGB agents during his tours in Moscow and Vienna - the female translator, identified as Violetta Sanni; Aleksiy G. Yefimov, known as ''Uncle Sasha,'' and Yuriy V. Lysov, known as ''George.''

Lonetree did ''plan and conduct meetings in Moscow and Vienna'' with the three, and ''Yuriy V. Lysov did appear on Dec. 27 and 30, 1986, for scheduled meetings with Sgt. Lonetree'' in Vienna, the charges state.

Lonetree ''did gather names and photographs of covert agents'' assigned to the embassy staff in Moscow and provide them to the KGB ''during the period September 1985 to December 1986,'' the charges say.

Lonetree ''wrongfully and intentionally (did) disclose information identifying covert U.S. intelligence agents, with the knowledge that the United States is taking affirmative measures to conceal such covert agents' intelligence relationship to the United States, by identifying by name and delivering photographs of covert United States intelligence agents to Aleksiy G. Yefimov, AKA 'Uncle Sasha,' an individual not authorized to receive classified information. ...''

Lonetree also allegedly ''did gather information regarding floor plans and office assignments for the embassies of the United States in Moscow, USSR, and Vienna, Austria,'' the Marine Corps charged.

Floor plans at the Moscow embassy were stolen during February 1986, while floor plans to the Vienna embassy were stolen during November, according to the charges.

Also while working in Vienna, Lonetree allegedly stole ''three photographs of some value, the property of the United States government,'' the charges said, but didn't elaborate on what type of photographs.

A Pentagon official, who requested anonymity, said Lonetree had caused serious damage, but he added that the damage was not permanent.

All told, Lonetree was charged with three specifications of conspiring to commit espionage, one of espionage, three of larceny and wrongful appropriation of government property, five of failing to report contacts with citizens of a Communist-controlled nation, and seven general charges involving such things as improper disclosure of national defense information or lying under oath when interviewed by investigators.

The one count of espionage, which carries the maximum penalty of death, concerns the allegation that Lonetree provided embassy floor plans and office assignments to the Soviets ''with intent or reason to believe that it would be used to the injury of the United States or to the advantage of the Soviet Union''

Maximum penalties for the other charges were not immediately available.