(Changes Marine group and length of extension after official correction by Marine Corps)

WASHINGTON, Aug 4 (Reuters) - More than 1,200 Marines deployed to train Afghan security forces have had their tours of duty extended by 26 days, the Marine Corps said.

Col. Dave Lapan said the Marines from the 2nd Battalion, 7th Marine Regiment will now remain in Afghanistan until Nov. 30. The Pentagon is also sending nearly 200 new support troops including helicopter units and teams specializing in clearing routes and disposing of explosives.

A defense spokesman had said earlier on Monday that the Marines were from the 27th Marine Expeditionary Unit and that their tours had been extended by 30 days.

Extended Marine tours come amid U.S. concern about rising violence in Afghanistan from the Taliban and other groups, including militants that U.S. military officials say are being trained and equipped at safe havens in neighboring Pakistan.

U.S. forces invaded Afghanistan in 2001 and toppled the Taliban government after the Sept. 11 attacks.

Last month, the Pentagon issued a one-month extension for some 2,200 Marines who deployed for combat duty in March from the 24th Marine Expeditionary Unit. That extended their stay from October to November. (Reporting by David Morgan; editing by Bill Trott and David Storey)

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