Reuters -- The United States has the military capacity to defeat any Iranian attempt to shut down sea commerce in the oil-rich Gulf region and will hold Tehran directly responsible for shipping disruptions, Defense Secretary Leon Panetta said on Wednesday.

"The United States is fully prepared for all contingencies here," Panetta told a Pentagon news conference. "We've invested in capabilities to ensure that the Iranian attempt to close down shipping in the Gulf is something that we are going to be able to defeat, if they make a decision to do that."

Panetta's comments came amid rising tensions in the region over Iran's nuclear program and its threats to close the vital Strait of Hormuz unless the international community revokes sanctions imposed on Iranian oil shipments.

A security team aboard a U.S. Navy oiler opened fire with a .50 caliber machine gun on a small boat off the United Arab Emirates this week after it failed to heed warnings to alter its course. An Indian fisherman was killed, and three others were wounded in the incident, which is under investigation.