WASHINGTON — Defense Secretary Leon Panetta said Wednesday that the United States was preparing for “threats” from Iran and Syria’s turmoil as an aircraft carrier headed to the region ahead of schedule.

The USS John Stennis and its strike group will set forth shortly for the Middle East, a deployment ordered four months ahead of time to minimize the gap in which the United States has only one carrier in the region.

Visiting the nuclear-powered carrier at its home base in the Pacific state of Washington, Panetta said that the accelerated deployment was meant to deal “with a lot of threats in the Middle East right now.”

“Obviously Iran is one of those threats that we have to be able to focus on and make sure that we’re prepared to deal with any threats that could emerge out of Iran,” Panetta told reporters.

“Secondly, it is the turmoil in Syria, and we’re obviously following that closely as well,” Panetta said.

Panetta said that the United States was also maintaining its force due to the risk of Iran blocking the Strait of Hormuz and amid the Arab Spring of revolutions, which “present both challenges and opportunities.”

Israel has not ruled out an attack on Iran to prevent the clerical regime from developing a nuclear weapon. Iran’s uranium enrichment has raised international suspicion, although Tehran says it is for peaceful purposes.

Iran has threatened to block the Strait of Hormuz, through which one-fifth of the world’s oil passes, in response to punishing US sanctions. But Iran has not made good on its threats even as the United States works to severely curtail its oil exports.

In Syria, the United States has demanded that President Bashar al-Assad step down amid raging violence that human rights activists say has killed more than 23,000 people since March 2011.

But the United States has little appetite for intervention in the turbulent country. Panetta, asked by a reporter about imposing a no-fly zone over Syria, repeated that the proposal was “not on the frontburner right now.”

President Barack Obama, however, has warned Assad of “enormous consequences” if his forces resort to chemical weapons.

The Stennis strike group, which was initially due to deploy at the end of the year to the Pacific, is relieving the USS Enterprise which is slated to be decommissioned.