Hanoi, Vietnam ? The U.S. is pressing Vietnam for underwater searches and access to aging witnesses in stepped-up efforts to recover remains of Americans missing from the Vietnam War, Defense Secretary Donald H. Rumsfeld said Monday.

“We still have work to do,” Rumsfeld said, though he added that he was pleased Vietnamese military officials had pledged in meetings with him to do more to help recover the remains.

Rumsfeld told reporters U.S. officials will work to see if the U.S. can provide technical assistance with underwater recovery efforts.

There are 1,805 American troops unaccounted for from the war, including 1,376 in Vietnam, according to Marine Maj. Jay Rutter, deputy commander of the Joint POW/MIA Accounting Command, which heads the recovery efforts here. Of those still missing, 453 were lost at sea or over water, according to the Pentagon data.