Alex Brandon, Associated Press
Auburn defensive back Jerraud Powers, left, can't break up the winning touchdown catch by LSU receiver Demetrius Byrd on Saturday.

BATON ROUGE, La. — Matt Flynn threw a 22-yard touchdown pass to Demetrius Byrd with a second left to lift fifth-ranked LSU to a 30-24 victory over No. 18 Auburn on Saturday night, keeping LSU's national title hopes alive and well.

With South Florida losing earlier in the week, LSU is certain to move up to at least third in the BCS standings, behind only Ohio State and possibly Boston College, which was idle this weekend.

Flynn finished with 319 yards passing and three touchdowns

Auburn's Brandon Cox, taking hits in the pocket but rolling out effectively when necessary, turned in a gutty performance, passing for 199 yards and a pair of touchdowns.

His last scoring pass, a 3-yard touchdown strike to Rodgeriqus Smith, gave Auburn a 24-23 lead with 3:21 to go.

But Auburn, following a game-long pattern of keeping the ball away from LSU returner Trindon Holliday, squibbed the kickoff, giving LSU the ball on its 42.

Flynn scrambled for 19 yards during the final drive, then took one more shot at the end zone as the clock wound down instead of getting the ball in the middle of the field to set up a potential game-winning field goal. He floated pass perfectly to the back of the end zone, where Byrd emerged from behind a defender and made a sliding catch, sending Tiger Stadium into a frenzy.

LSU extended its winning streak in Death Valley to 18 games. If that streak had been snapped, it would have been fitting if Auburn was the team to do it. Auburn came in on a three-game winning streak that included impressive road wins over No. 14 Florida and Arkansas.

LSU's Jacob Hester gave LSU a 20-17 lead, diving for the pylon on early in the fourth quarter after catching a swing-pass on third-and-goal for the 5. He led a patient rushing attack that amassed 169 yards, all but 40 in the second half.

Auburn led 17-7 at halftime after getting touchdowns on Cox's 17-yard pass to Montez Billings and Carl Stewart's dive over the pile, which was set up by LSU backup quarterback Ryan Perrilloux's fumble.

Flynn led LSU back with help from his best receiver, Early Doucet, back from a groin injury that had caused him to miss most of the last five games. Doucet made several clutch catches, finishing with seven receptions for 93 yards.