(CNN) -- Even as U.S. military officials privately maintain there are no immediate plans for action against the Syrian regime, the American presence next door in Jordan is quietly growing as is an increased U.S. military capability to defend that nation.
U.S. military assets either in place or due to arrive include:
Defense Secretary Chuck Hagel's approval to keep a Patriot missile battery and a detachment of F-16s there indefinitely adds about 400 troops to the U.S. presence.
While the units officially support U.S.-Jordanian military cooperation, they provide a real capability in a crisis.
The Patriot battery would be used to defend Jordan against any missiles launched from Syria. The F-16s "send a message" to Syria, says one senior U.S. military official, that the United States will defend Jordan, if needed.
Another 200 or so troops specializing in military planning from the 1st Armored Division's headquarters will arrive later this summer.
They are to replace existing planners with a more focused ability to help Jordan's commanders prepare for any number of Syrian contingencies, including a chemical weapons crisis or a worsening refugee situation.
The Navy also continues its longstanding deployment of three anti-ballistic missile ships is the eastern Mediterranean. The ships, with a total crew of about 1,000, carry Tomahawk cruise missiles to defend Israel from any attack by Iran.
Several Navy officials say they could also readily defend Jordan or Israel against any Scud missile launch from Syria.
The Marines are continuing a longstanding presence of about 130 personnel to train Jordanian units that are slated to go to Afghanistan. But that counter-terrorism training could be used in any crisis, officials acknowledge.
Army Airborne exercise
All of the efforts were put into place before President Barack Obama said last week the United States had concluded the Syrian regime of President Bashar al-Assad had used chemical weapons against its people.
Senior U.S. officials have said there is continuing concern that eventually some type of military units will be needed to go into Syria to take control of the weapons. For more than a year, the United States has quietly trained Jordanian forces for that mission.
But the Army's 82nd Airborne Division is also training for that scenario.
In a series of exercises at Fort Bragg, North Carolina, planned for next week, a brigade will train on how to be ready to deploy from the United States in 18 hours for a chemical weapons crisis.
Although long planned, the exercise is aimed at what commanders see as a real world scenario, a division official says.
At last Wednesday's White House meeting of senior national security officials, the question of whether to consider imposing a "no-fly" zone over Syria was again discussed, according to a military official who did not attend the meeting but was briefed about it.
He said Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff, continued to raise concerns about the need to be certain about clear objectives and complete understanding of the risks to pilots and the overall potential consequences of that action.
Dempsey has warned that the notion of a limited "no-fly" zone would pose great risk to aircrews because of a sophisticated Syrian air defense system.