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NATIONAL HARBOR, MARYLAND --  the service's number two officer confirmed Monday -- but if Congress can't pass the defense appropriations bill, it may be unable to pull the trigger.

Speaking at the Navy League's Sea-Air-Space conference, Assistant Commandant of the Marine Corps Gen. Glenn Walters said that if the Defense Department must instead contend with a yearlong continuing resolution, keeping funding flat, the service won't be able to execute its new plan to contend with emerging threats.

"People forget that the world just changes frequently now," Walters said. "We are seeing UAS threats in the Middle East right now that we had not seen last year, which means we didn't have a program for it last year. Which means if we have a CR this year, we can't use the money and counter the threat, and that's a challenge."

Asked by Military.com to expand on what counter-UAS strategies and technologies the Marine Corps would like to invest in, Walters confirmed the service does have a plan, but declined to elaborate further.

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The Corps has conducted multiple experiments to defend against and eliminate enemy drone technology. In the fight against the Islamic State in the Middle East, enemy fighters have used small, commercially available quadcopters and similar aerial drones to conduct surveillance and, with modifications, to drop grenades and other explosives on ground troops.

Last fall, Marine Corps Special Operations Command made a plea to industry to showcase technology that would help operators counter this insidious threat.

"Our focus right now is not so much counter-UAS on a larger scale, but counter-small systems," Master Sgt. Justin Olson, an operator with the command, said at the time. "Your micro, small handheld stuff, what will the enemy use."

In a December wargame on the West Coast, Marines from 1st Light Armored Reconnaissance Battalion purchased commercially available quadcopters so they could practice both hiding from and evading them on the battlefield and shooting them down using mounted machine guns.

The Marine Corps has also reportedly conducted field tests with Battelle's DroneDefender, a new man-portable device that can be aimed at enemy UAS and used to bring them down by interrupting the frequencies on which they operate. Battelle has sold a small number of the devices to the military and the Department of Homeland Security, and is working to develop a smaller and more capable version of the device.

"If you need something new, you want new capabilities to counter something that the enemy has, it's very difficult under CR to do that," Walters told Military.com. "It doesn't mean it's impossible, but it means a delay in maybe getting it."

Congress has until April 28 to pass the 2017 National Defense Appropriations Act, averting a yearlong CR. The Marine Corps has previously warned that it will have to cease most flight operations in July 2017 under a CR, and Navy officials have said the service will have to shut down two carrier air wings if funding remains flat for another year.

-- Hope Hodge Seck can be reached at hope.seck@military.com. Follow her on Twitter at@HopeSeck.