WASHINGTON U.S. Defense Secretary Robert Gates said on Monday all options for dealing with Iran must remain open and called for international pressure and tougher sanctions to curb Tehran's nuclear aspirations.
"With a government of this nature, only a united front of nations will be able to exert enough pressure to make Iran abandon its nuclear aspirations -- a source of great anxiety and instability in the region," Gates said in speech to the Jewish Institute for National Security Affairs.
"Our allies must work together on robust, far-reaching, and strongly enforced economic sanctions," he said, also noting a need for political and diplomatic pressure.
"And, as President (George W.) Bush has said, with this regime, we must also keep all options on the table," said Gates in comments prepared for delivery to the nonprofit group that advocates a link between U.S. and Israeli security interests.
The United States and other Western nations fear Iran is trying to develop nuclear weapons under the cover of a peaceful nuclear energy program. Iran denies it wants nuclear weapons.
Washington and Tehran also are at odds over Iraq, where U.S. officials say Iranian agents are providing deadly technology and training to insurgents. Iran dismisses those charges as well.
The U.N. Security Council has passed two sanctions resolutions against Iran for failing to halt uranium enrichment. World powers have agreed to delay further sanctions until November to see whether Iran's agreement with U.N. nuclear inspectors to clear up questions about its program yields results.
The United States has said major powers must take a concerted, multilateral approach toward further sanctions, and that the approach should involve banks and companies.
Among a string of U.S. objectives in the Middle East, Gates listed an Iran that does not build nuclear weapons or "hold Israel hostage with the threat of attack."
Gates' comments come as Israel's new defense minister, Ehud Barak, visits Washington to promote joint anti-missile projects designed to intercept missiles of the kind deployed by Iran and Syria.
Gates and Barak are to meet privately on Tuesday and the Pentagon chief will host a dinner for the minister that evening.