The board of governors of the U.N.'s nuclear watchdog agency is meeting in Vienna, where it is expected to vote on a measure further criticizing Iran for its nuclear program.

The board is taking up a draft resolution that expresses “deep and increasing concern” that Tehran's atomic activities are leading to toward the development of nuclear weapons. However, it stops short of referring the matter to the U.N. Security Council or setting a deadline for Iran to comply.

The board meeting of the International Atomic Energy Agency comes about a week after it alleged there is “credible” evidence that Iran is trying to build nuclear warheads.

Iran has denied the allegations and says its nuclear program is peaceful. Iran's IAEA envoy, Ali Ashgar Soltanieh, has accused the agency of leaking secret information about his country's nuclear program that has jeopardized the lives and safety of its scientists.

The resolution was crafted by the U.S. and five other world powers .

On Thursday, the U.S. IAEA envoy said, after ten years of probes, the agency's information indicates Tehran has carried out activities “relevant to the development of a nuclear explosive device.” Glyn Davies also said Iran had chosen to “denigrate” the IAEA and its methodology instead of addressing concerns. He commented in a letter to the agency's 35-member board.

Recent Israeli media reports have said the government has been considering a military strike on Iran's nuclear sites.

But U.S. Defense Secretary Leon Panetta, before a meeting Thursday with Israel's defense minister, cautioned Israel not to take military action against Iran.

The U.N. Security Council has passed four sets of sanctions on Iran for refusing to stop nuclear activities that have both civilian and military uses.