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“Iran must cooperate with this investigation. Russia will assist in this investigation by any available means. Russia remains committed to a dialogue with Iran on the nuclear issue, and urges Iran to provide proof of its commitment to a peaceful nuclear program by the Oct. 1 meeting,” the Kremlin said.

Mr. Obama did not inform Mr. Hu on Tuesday of plans to go public with the information about the Iranian site, apparently because the White House had not yet decided to do so.

The Chinese on Thursday reiterated their opposition to new sanctions against Iran, but White House officials said Friday that Beijing made those comments before it had been briefed by U.S. intelligence officials.

“China is just now fully absorbing these latest revelations. I think we should stay tuned for the Chinese position in the coming days,” an adviser to Mr. Obama said.

A senior White House adviser told reporters here Friday that the development “increases our leverage diplomatically, and we intend to make use of it.”

“It was important to us, coming into this critical period in the fall, to be prepared, to be basically in the driver’s seat under any contingency,” an official in Washington said.

Barbara Slavin and Eli Lake in Washington and Nicholas Kralev in Berlin contributed to this report.