The Pentagon would not specify the location but a senior military official said it would arrive "relatively soon."
The decision follows an announcement earlier in the week that the U.S. would deploy a carrier strike group and bomber task force to the region in response to indications that Iran and its proxies were preparing to attack U.S. forces and interests in the region.
In addition to the Patriot system, the amphibious transport dock ship USS Arlington will also head to the Middle East. The Arlington will replace the USS Fort McHenry, as part of the USS Kearsarge Amphibious Ready Group. A senior military official told reporters the Arlington was already slated to eventually be in the region, but its movement will be expedited to provide enhanced command and control capabilities. The Kearsarge transited out of the Persian Gulf on Tuesday, but will remain close by.
"The Department of Defense continues to closely monitor the activities of the Iranian regime, their military and proxies," the Pentagon said in a statement, adding, "The United States does not seek conflict with Iran, but we are postured and ready to defend U.S. forces and interests in the region."
The Patriot battery provides long-range defense to counter tactical ballistic missiles, cruise missiles, and advanced aircraft. In late September 2018, the Pentagon decided to shift four Patriot systems out of the Middle East, as part of a "re-balancing" to counter threats from China and Russia.
The senior military official said U.S. intelligence had seen "some anomalous naval activity by Iranian regime vessels" to include commercial vessels, known as dhows, being operated by Iran's Islamic Revolutionary Guard Corps. Those vessels were "loaded with potential military hardware to include missiles," the official said.
The threat toward U.S. forces and interests is "on land and sea," the official continued, adding that in Iraq and Syria Shiite militias could be operating on behalf of Iran to carry out these potential attacks.
"There's been no change in the urgency of the threat" since Sunday's announcement that the U.S. would send a carrier strike group and bomber task force, the official said. However, the official would not provide details as to whether Iran had changed its behavior in the last week.
The USS Abraham Lincoln carrier strike group transited the Strait of Hormuz on Thursday from the Mediterranean Sea. Also this week, four B-52 bombers arrived at Al Udeid Air Base in Qatar.
"It's important that Iran understand that an attack on Americans or its interests will be met with an appropriate response," Acting Defense Secretary Patrick Shanahan told reporters on Friday.