The State Department and the Israeli government denied yesterday that the United States has asked to inspect Israel's secret nuclear installations to verify that American-made timing devices have not been used to make atomic weapons.

However, U.S. and diplomatic sources confirmed that the United States had called on Israel to account for the location and use of the estimated 500 to 600 devices, which were not licensed for export and which Israel apparently obtained surreptitiously. The sources also confirmed that the United States has asked Israel to return any unused devices, known as krytrons.

The department publicly refused comment on a Washington Post report yesterday about these requests. However, a department official, who spoke with reporters on condition that he not be identified, said the United States had not asked to inspect nuclear installations in Israel.

The sources, while acknowledging that was technically correct, said the United States was seeking physical proof of where the krytrons are located. As one said: "That means Washington wants Israel either to put the devices on a table for U.S. officials to count or else take the Americans to the specific locations, whether nuclear or nonnuclear, where the devices are stored or in use."

The Israeli defense ministry acknowledged Sunday that a number of krytrons were in its possession and said they had been used for nonnuclear purposes. The statement was made after Newsweek reported that a U.S. grand jury in Los Angeles is investigating whether the devices were smuggled in violation of U.S. export laws.