Rivers broke a fourth-quarter tie with a 14-yard touchdown pass to Antonio Gates, then followed with a drive that ate up more than seven minutes and ended in a field goal, giving San Diego a 20-17 victory yesterday that keeps the Chargers rolling and the Cowboys reeling with the playoffs approaching.

San Diego (10-3) won its eighth straight and is on the verge of clinching the AFC West. The Chargers are 16-0 in December since Rivers became their starting quarterback.

“You don’t want to fade out in December, you want to be peaking,’’ Rivers said. “We’ve been able to do that the past few years. We just hadn’t sustained it into January. Hopefully this will be the year we keep this thing going into 2010.’’

San Diego’s last 11 December wins have come under Norv Turner, whom Cowboys owner Jerry Jones decided not to hire last time his head coaching job was available. Jones picked Wade Phillips instead and hasn’t gotten his money’s worth in December: 3-8 after this loss.

Players talked all week about wanting to win to boost Phillips’s job security, but they kept failing during pivotal moments on offense and defense.

Now the Cowboys (8-5) are stuck with consecutive losses for the first time this season, and are headed to New Orleans to face the undefeated Saints Saturday night. They also might be without star linebacker DeMarcus Ware, who was hospitalized after spraining his neck during the fourth quarter.

“Even though it might not look like we’re playing the best football, you can turn that around in a hurry,’’ Romo said. “I suspect this football team will do that.’’

Although this game was decided late, it tilted in San Diego’s favor in the first half, when the Chargers held the Cowboys to one field goal over drives that featured first downs 16, 3, and 27 yards from the end zone.

Dallas tied it at 10 on the final play of the third quarter, with Romo capping a 99-yard drive with a 6-yard touchdown pass to Miles Austin. Soon after, play was halted for several minutes because Ware was sprawled on the turf after ramming the crown of his helmet into the leg of a San Diego lineman.

Forced into third and 12 from his 47, Rivers responded with a 39-yard pass to Vincent Jackson, then the go-ahead touchdown pass (the 100th of his career) to Gates on the next snap.

After Romo failed to answer, the Chargers iced the victory by using 7:17 on a 15-play drive that ended with a 34-yard field goal by Nate Kaeding. LaDainian Tomlinson had nine of his 21 carries, and 27 of his 50 yards, on that series.

“There’s nothing more gratifying than to do it like that,’’ Tomlinson said.

Trailing by 10 with 1:56 left, Romo managed to get a touchdown - but it came with two seconds left. Gates then caught an onside kick attempt.

Romo was 19 of 30 for 249 yards, two touchdowns, and no interceptions, but still fell to 5-10 in December.