Washington ? Condoleezza Rice flexed America’s muscles in the Middle East Thursday, forcefully warning Iran the U.S. won’t ignore threats and will take any action necessary to defend friends and interests in the Persian Gulf.

A fresh Iranian missile test prompted a show of force from Israel as well.

Rice said Iran’s leaders should understand that Washington won’t dismiss provocations from Tehran and has the ability to counter them. “I don’t think the Iranians are too confused, either, about the capability and the power of the United States to do exactly that,” she said.

Though the White House has repeatedly asserted it prefers diplomacy to war, Rice used some of the administration’s most direct language yet to make clear the U.S. is strengthening its military presence to counter Iran in the strategic Gulf region and is prepared to use force. She also referred to U.S. arms sales to Gulf allies and military aid to Israel as protections against any threat from Iran.

“We take very, very strongly our obligation to help our allies defend themselves, and no one should be confused about that,” Rice said in Tbilisi, Georgia, before returning to Washington from a trip to Eastern Europe.

The chairman of the Joint Chiefs of Staff, Adm. Mike Mullen, noted Iranian testing of a longer-range missile, representing a “capability that raises the ante in the long run in that part of the world.”

Asked on a trip to Afghanistan whether the U. S. had strengthened its position, he said, “We have a very robust presence in that part of the world, have had for some time, and we’re robust enough to be able to adjust constantly, which is what we do, and we also try not to be very predictive about where we go and when we go and what we do there.”

Rice’s remarks were part of a rising rhetorical and strategic face-off between Iran on one side and the United States and Israel on the other. The posturing has raised concerns worldwide about a possible shooting war.

The most likely scenario for that would be an Israeli strike to reduce or eliminate the threat that Iran could soon field a nuclear weapon. Israel could theoretically launch an air strike against one or more of Iran’s known nuclear sites and at least set back the timetable for a bomb.

Israel has announced no such intention, although neither it nor its U.S. protector will rule out the possibility and Israel has sent multiple signals that it is ready to defend itself.

On Thursday, Israeli Defense Minister Ehud Barak said his country “proved in the past that it won’t hesitate to act when its vital security interests are at stake.”