The United States is seeking help from other countries to find out what may have happened to Robert Levinson, a former FBI agent missing in Iran, State Department spokesman Sean McCormack said on Wednesday.

"We are, starting today, going to approach other governments that have diplomatic relations with Iran to see if they know anything about Mr. Levinson's welfare and whereabouts and also to make inquiries on his behalf as well," McCormack said.

"Perhaps there is information that they might have. Perhaps they are able to find out information through their own resources on the ground there about Mr. Levinson's whereabouts," McCormack said.

The reason to ask for help from other countries is due to Iran's failure to provide "any substantive information," the spokesman said. He did not name what countries have been asked.

Washington has tried three times through Switzerland to ask Iran to provide information about Levinson's whereabouts since March 12, McCormack said Monday.

Washington has no diplomatic relations with Tehran since April 1980, five months after Iranian students occupied the American embassy in Tehran. Fifty-two Americans were held hostage for 444 days.

Robert Levinson, a Florida resident, reportedly went missing while on a visit to the Gulf island of Kish in Iran early in March.