A U.S. military official Thursday said Vietnam has not replaced the 20,000 troops it withdrew from Cambodia, despite charges by some Thai and Western officials that the pullouts were mere troop rotations.

"The 20,000-man pullout was real," said Maj. Timothy J. Pfister, spokesman for the U.S. Pacific Command. Citing intelligence reports, Pfister said, "It was a troop withdrawal, not a rotation and, so far, it has held."Prior to the troop withdrawals in 1985 and 1986, observed by Western reporters, senior Thai officials predicted the troops would be replaced quietly.

Vietnam has pledged to remove all of its troops from Cambodia by the end of 1990. If it can reach a political settlement with three guerrilla factions fighting the Phnom Penh government, the withdrawal will come earlier, Vietnam has said.