The Virginia House of Delegates gave initial approval yesterday to raising the drinking age to 21 -- but only if Congress does the same for personnel on military bases in Virginia.

The military-base amendment is an attempt to rebuke the federal government, which has threatened to start cutting off some highway money to any state that doesn't set the drinking age at 21 by 1986. The bill passed on a 51-to-43 vote and faces a final vote today.

The Senate had a chance to add the same amendment to its drinking-age bill Tuesday but declined, 19-to-16, before passing the bill.

In the House, the great bulk of delegates with one or more of Virginia's many military bases in their districts and those frustrated by the federal "blackmail" prevailed.

"I'm prepared to bow to the will of the federal government" about the highway funds, said Del. Warren G. Stambaugh (D-Arlington), who introduced the amendment and who has opposed similar bills in the past. "They're the big boys up there."

But if the drinking age is going to be 21 in Arlington County, where there are several military facilities, "it should be 21 in all of Arlington County," he said.

The House bill would raise the beer-drinking age to 20 on Oct. 1 and to 21 a year later. The legal age for drinking wine and liquor is 21.

Without the amendment, "you create two classes of citizens in the Tidewater area -- one military and one civilian," said Majority Leader Thomas Moss (D-Norfolk), whose district is home to the largest naval base in the country.

The sponsor of the bill, Del. Frank Hargrove (R-Hanover), pleaded with the House not to accept the amendment. "We all know we have no authority over military reservations," he said