Republican Rep. Paul S. Trible Jr. of Virginia said he has secured almost $1.2 million for his U.S. Senate race, maintaining a sizable fund-raising lead over his Democratic opponent, Lt. Gov. Richard J. Davis.

Trible's announcement, which came as Democratic Gov. Charles S. Robb prepared to host a $2,000-a-couple Davis fund-raiser at the City Tavern Club in Georgetown last night, placed the Newport News congressman far ahead of the $450,000 that Davis aides said they have raised to date.

Officials of the Davis campaign, which had collected only $32,000 to Trible's $521,000 earlier in the summer, declined yesterday Trible's challenge to release financial details comparable to those disclosed by the Republican camp. But the Democrat's campaign aides said that Davis, who was drafted as his party's nominee in June, is keeping pace with the GOP fund-raising efforts despite his relatively late start. "In less than eight weeks we have cut the gap from 16-to-1 to 3-to-1," said James Carville, Davis' campaign manager. "We're encouraged by our own efforts."

According to documents released by the Trible campaign, the Republicans have raised almost $925,000, approximately$404,000 of it over the past seven weeks. About $162,000 of the money raised since the first week of July came from a wide range of groups, including the National Conservative Political Action Committee (NCPAC) and political action committees representing the tobacco industry, defense contractors, power companies, home builders and paper manufacturers.

Included in the almost $1.2 million claimed by Trible is $275,000 worth of in-kind contributions expected from the Republican Party before the November election.

"Obviously we are pleased with the money we have raised," said Neil Cotiaux, Trible's press secretary. "It shows momentum, and it shows that 6,500 individuals as well as numerous business and professional organizations believe that Paul Trible is the best candidate."

Republicans have targeted Virginia's race as one of the most crucial U.S. Senate contests this year, and Trible's financial announcement served to reinforce expectations for a GOP media blitz after Labor Day. Trible, who is not well known outside his Tidewater congressional district, has already been running television and radio advertisements around the state, heralding endorsements from Republican Sen. John Warner and Virginia's GOP Reps. G. William Whitehurst, Thomas J. Bliley Jr., J. Kenneth Robinson and M. Caldwell Butler.

Davis, who won his lieutenant-governor seat just last year, has not yet begun broadcasting any radio or television ads, and aides to the 60-year-old former Portsmouth mayor said such early advertising is unnecessary.

Among committees listed as making big donations to Trible were groups representing Tenneco Inc., whose Newport News shipyard is the largest employer in Trible's congressional district, with $5,000; and such defense contractors as Boeing Co., $500; Sperry Corp., $500, and Lockheed, $500.

As a three-term congressman from Newport News, the 35-year-old Trible has been a staunch advocate of defense expenditures as a member of the House Armed Services Committee.

Also among Trible's donors were PACs representing R.J. Reynolds and the Tobacco Institute, which gave Trible contributions totalling $2,000. Trible voted against the Reagan tax program last week, saying he felt the planned doubling of the federal tobacco tax placed an unfair burden on Virginia.

Davis supporters said the lieutenant governor, who had been reluctant to enter the race because of fears of money troubles, is still optimistic about meeting his goal of $1.5 million, or about $500,000 less than Trible expects to raise. "We won't meet them toe to toe," said Davis fund-raiser William G. Thomas, "but unsuccessful GOP gubernatorial candidate Marshall Coleman spent $500,000 more than Robb last year, and I don't think that $500,000 did him much good."