The dispute over Iran's nuclear program is a major test for the NATO alliance and its ambition to play a greater role in global security, European and US officials told a trans-Atlantic security conference Saturday. Richard Holbrooke, a former US envoy to the United Nations and the Balkans, said Iran lay "at the center (of a) genuine global crisis." Russia and China may resist U.N. sanctions against Tehran but "a nuclear Iran is just as much, if not more, dangerous to them" as it is to Israel, Western Europe and North America, he told the Brussels Forum - a gathering where 275 trans-Atlantic politicians, business leaders and other experts debated global security. Speaking at the same panel discussion, Javier Solana, the EU security affairs chief, said Iran was a destabilizing factor, but stressed the United States and EU governments were not contemplating military action. "We are not thinking of that," Solana said, adding diplomatic efforts to get Tehran to comply with its nonproliferation commitments had not been exhausted. US President George W. Bush has said in the past, however, that the use of military force remains an option.