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CNN —  

The Pentagon has identified two warships, hundreds of vehicles, dozens of aircraft and more than 400 troops that could made available for hurricane relief in the next 24 hours, according to several defense officials.

The Defense Department had not received any official requests for help from Texas as of midday Monday, but is still identifying resources that could be used, the sources said. Officials say a request for assistance could come at any moment.

Those resources include the USS Kearsarge and the USS Oak Hill, which are being readied for possible deployment to Texas if active duty military help is requested by the state. Kearsarge is in the Atlantic Ocean for training, but will return to Norfolk Tuesday. It will load up with disaster relief supplies like water and food, and possibly a unit of Marines if needed, according to a Navy official.

The Oak Hill, a smaller ship, will also begin loading on supplies in Norfolk in case it is called upon, the official said.

“We have no official tasking yet,” one defense official told CNN.

Military forces cannot operate in the US without proper authority, the official noted, a “task” order from FEMA and state authorities is required before action. Without official orders, the Pentagon is limited to prepositioning equipment and people and issuing “24-hour prepare-to-deploy orders,” officials said.

“Active duty units are en route to the staging area in anticipation of a possible request. There has been no formal tasking,” of active duty units, Pentagon spokesman Col. Robert Manning told reporters.

A FEMA spokesperson said that the agency is working with the Pentagon and state officials to identify needs, and a Pentagon liaison has been placed in the Regional Response Coordination Center, and Defense Department and US Northern Command personnel have been placed in the National Response Coordination Center in Washington.

Those personnel will “facilitate (Defense Department) support for requests from the state that are best addressed by their unique capabilities and resources,” the spokesperson said. “Once state and local officials exceed their capacity to address specific needs, they request additional support through FEMA.”

Twelve Defense Department military helicopters and aircraft able to conduct aerial surveillance and search and rescue have been already prepositioned in Texas. More than three dozen additional aircraft have been identified. In addition more than 200 high-wheeled tactical vehicles capable of moving through high water have been identified as available and ready to move within 24 hours.

These vehicles could readily be used for water rescue, officials say.

Military surgical teams, communications teams, maintenance and other military support elements totaling more than 400 personnel are also on orders to be prepared to deploy within 24 hours.

A Marine Corps reserve amphibious assault battalion and a Marine Corps reserve reconnaissance battalion equipped with small boats stationed in Texas are in the early stages of planning what they can offer for assistance as well, according to a Marine Corps official.

Because Texas has a large National Guard and has already devoted thousands of troops and hundreds of vehicles to the rescue effort, it is not clear if the state will actually make the additional requests for federal help, one of the officials said.

However, on Sunday, the Defense Department and Texas Gov. Greg Abbott agreed to establish a “dual status command” that would allow a single commander for both federal and state forces overseeing and coordinating the response efforts.

“It is imperative that we give our military and first responders on the ground the most efficient method of execution when responding to the urgent needs of Texans,” Abbott said in a statement. “The dual status command will ensure that the Texas National Guard is overseeing all response efforts in a way that most closely coordinates with federal troops and military efforts to ensure the needs of the victims of Hurricane Harvey are being met as swiftly and effectively as possible. I thank (Defense) Secretary (James) Mattis for his cooperation and immediate response to our request and continue to assure the people of this state that Texas is doing everything possible to aid in your time of need.”

With the entire Texas National Guard now activated, there are 16 aircraft and personnel conducting day and night wide-area search-and-rescue missions along the Texas coast, from Corpus Christi to Houston.

The New York Air National Guard has provided one C-130, three HH-60s, and two C-17s. There are also six helicopters from Utah, the Nebraska and North Carolina Army National Guards, seven fixed-wing aircraft from the US Coast Guard and the US Air National Guard, and the Texas National Guard is using about 200 Humvees and 200 high-water vehicles.

CNN’s John Kirby contributed to this report.