U.S. should use all tools to pressure Iran: Obama

WASHINGTON (Reuters) - Democratic U.S. presidential candidate Barack Obama said on Tuesday preventing Iran from acquiring a nuclear weapon was in America's vital interests and vowed to use all tools to pressure Tehran.

"No tool of statecraft should be taken off the table," Obama said in a speech covering broad national security issues, including Iraq and Iran.

"I will use all elements of American power to pressure the Iranian regime, starting with aggressive, principled and direct diplomacy -- diplomacy backed with strong sanctions and without preconditions," Obama said.

Obama's rival in the November election, Republican John McCain, has criticized past statements by the Democratic candidate indicating a willingness to talk directly to officials such as Iranian president Mahmoud Ahmadinejad.

While promising "tough negotiations" in coordination with U.S. allies, Obama was cautious about whom he would meet with in Iran, saying that "if it will advance our interests" he would meet with the appropriate leader at a time and place he deems appropriate.

(Reporting by Caren Bohan, editing by Patricia Zengerle)