The top U.S. general in the Middle East called Iran the "greatest threat" in the region, but said only an internal uprising could halt its nuclear weapons program.
American military strikes could delay Tehran's pursuit of atomic weapons, but "only the Iranian people can stop this program," U.S. Central Command Chief Gen. James Mattis told lawmakers Tuesday.
Mattis described an increasingly aggressive Iran that is actively working against Washington across the Middle East. Mattis says economic sanctions have yet to dissuade Iran from pursuing nuclear weapons.
But the general many regard as a "warrior-scholar" also endorsed allowing the sanctions' pressure to mount on Iranian leaders and said now is not the time for U.S. military action.
"I don't see this going in the right direction until sanctions" have been fully implemented, he said.
The sanctions might bring officials in Tehran to scrap the nuclear arms program because "this is a country that has few allies," Mattis said. "And I don't count that little fellow down in Venezuela," he added, taking a swipe at Venezuelan President Hugo Chavez.
While most of the world is focused on Iran's nuclear arms ambitions, Mattis described a much broader Iranian irritant.
Tehran is actively working to fan the flames of instability in places like Yemen, Bahrain, Kuwait and other nations, Mattis said. "They enjoy this sort of thing," he added.
U.S. officials also believe Tehran has supplied the embattled Syrian regime with air defense systems, intelligence gathering and communications equipment, as well as other items for its fight against opposition fighters.
"We see what they are doing in [Syria], and they know their link to Hamas will be cut off if Assad falls," Mattis said, referring to the Syrian President Bashar al-Assad.
Connecticut Sen. Joseph Lieberman has concluded Iran's goal is to become the dominant nation in the Middle East.
Mattis suggested there is a brewing power balance struggle emerging in that area of the globe, saying: "The whole region has become aware and is plotting a strategy" to blunt Iran's growing influence.
Some hawkish GOP lawmakers, like Arizona Sen. John McCain, believe "the sanctions have done nothing to stop the Iranian nuclear program."
In usually blunt fashion, McCain asked Mattis whether tougher sanctions implemented in recent months had done anything to make the general believe Iran is even thinking of abandoning its nuclear efforts. The Marine Corps general replied: "No, sir, I have not seen that."
As Mattis was urging patience for sanctions to further squeeze Tehran, Defense Secretary Leon Panetta was across town addressing an Israeli-American political action committee with tough words for Iran.
Panetta said Obama administration officials "want diplomacy to work," but he also continued to be characteristically muscular in his rhetoric about an American military strike.
"We will keep all options -- including military action -- on the table to prevent them from obtaining a nuclear weapon," Panetta said. "Let me be clear: we do not have a policy of containment. We have a policy of preventing Iran from acquiring nuclear weapons."
The mixed messages from senior military leaders is the latest instance of an intricate game of cat-and-mouse Obama administration and Pentagon officials have been playing for months about what Washington will do to thwart Tehran's nuclear ambitions.