UNITED NATIONS — The deepest freeze in U.S.-Russia relations since the Cold War has brought diplomatic efforts to halt Iran's nuclear ambitions to a halt just as Western governments and U.N. inspectors are warning that Tehran could be gaining the ability to build a nuclear weapon.

Russia this week pulled out of a six-nation meeting scheduled for Thursday to discuss further sanctions against Iran, freezing for the time being a 3 1/2-year old diplomatic campaign to persuade Tehran to abandon uranium enrichment.

Neither the United States nor Israel has ruled out attacking Iran's nuclear facilities, although there are no overt signs that planning for a military strike has intensified. » read more

WASHINGTON — World powers agreed Monday to toughen U.N. sanctions against Iran after the Islamic Republic failed to accept by the weekend deadline a proposal aimed at resolving the crisis over its nuclear program, the State Department said Monday.

"We are disappointed that we have not yet received a response from Iran," State Department spokesman Gonzalo Gallegos said. "We have no choice but to pursue further measures against Iran."

The decision by Britain, China, France, Germany, Russia and the United States came after a senior Iranian general warned that if attacked, Iran "easily" could block the Strait of Hormuz, the Persian Gulf passage through which 40 percent of the world's petroleum supplies are shipped. » read more