Mark McGwire's back is acting up again, opening the way for Sammy Sosa to grab the lead in the homer race.

McGwire, stuck on 62 home runs, hoped to be in St. Louis' lineup tonight when his Cardinals faced Pittsburgh. He was lifted after just two at-bats Sunday night in Houston after complaining of minor back spasms."It's all right," McGwire said after the Cardinals rallied for a 3-2 victory over Houston.

"We'll just have to wait and see," manager Tony La Russa said.

The last time McGwire's back stiffened up, on June 1, he missed three days.

McGwire hasn't homered since getting No. 62 on Tuesday night when he broke Roger Maris' 37-year-old record. Since then, he's 1-for-14 in five games, the one hit a single Friday night in Houston.

Sosa, meanwhile, has four home runs in his last three games, including a pair Sunday to tie McGwire at 62.

"It's awesome, outstanding," McGwire said of Sosa's spurt. "I've been doing this for the last few years with Ken Griffey. We go back and forth."

McGwire said he didn't believe reaching No. 62 and pulling four ahead of Sosa at the time meant an end to the race.

"We've got until the 27th of September," he said. "I don't think you have to be a rocket scientist to figure out it's not over. I never once thought that was it."

McGwire, who in May led Sosa 24-9, said he left a congratulatory telephone message with Sosa after the Cubs slugger tied him.

"He's having an unbelievable year," McGwire said. "He got hot this weekend and hit a bunch out. He's got 62 and it's awesome. We're all sitting there watching and it's a pretty thing for the game of baseball."