MIAMI — LeBron James led a title-saving charge, and now his crown will be on the line one more time in Game 7. James powered Miami to a frantic fourth-quarter rally and overtime escape as the Heat beat the San Antonio Spurs 103-100 on Tuesday night to extend the NBA Finals as far as they can go and keep their repeat chances alive. Losing his headband but keeping his cool while playing the entire second half and overtime, James finished with 32 points, 10 rebounds and 11 assists, making the go-ahead basket with 1:43 remaining in the extra period. Tim Duncan scored 30 points for the Spurs, his most in an NBA Finals game since Game 1 in 2003, but was shut out after the third quarter. He added 17 rebounds. Game 7 will be here Thursday, the NBA's first do-or-die game to determine its champion since the Lakers beat the Celtics in 2010. The Spurs looked headed to a fifth title in five chances when they built a 13-point lead with under 4 minutes left in the third quarter, then grabbed a five-point edge late in regulation after blowing the lead. But James hit a 3-pointer before Ray Allen tied it with another with 5.2 seconds remaining in regulation. James was just 3 of 12 after three quarters, the Heat trailing by 10 and frustration apparent among the players and panic setting in among the fans. Nothing to worry. Not with James playing like this. He finished 11 of 26, even making a steal after his basket had given Miami a 101-100 edge in the OT. Before that, he was 12 minutes from hearing the familiar criticisms about not being able to get it done, from having to watch a team celebrate on his home floor again. Then he changed the game and erased that story. The Heat, who haven't lost consecutive games since Jan. 8 and 10, had too much defense and way too much James for the Spurs in the final 17 minutes. They are trying to become fourth team to win the final two games at home since the NBA went to the 2-3-2 format for the finals in 1985. James came in averaging 31.5 points in elimination games, highest in NBA history, according to a stat provided through the NBA by the Elias Sports Bureau. This wasn't quite the 45-point performance in Game 6 of last year's Eastern Conference finals in Boston, but given the higher stakes may go down as more important — if the Heat follow it with another victory Thursday. The Heat were in the same place as they were in 2011 at the end of their Big Three's first season together, coming home from Texas facing a 3-2 deficit in the finals. This is a different team. And oh, what a different James. They said they welcomed this challenge, a chance to show they how much mentally tougher they were than the team the Dallas Mavericks easily handled in Game 6 that night. James made sure they did, looking nothing like the player who was so bad in the fourth quarters during that series. He was simply unstoppable down the stretch of this one. Kawhi Leonard had 22 points and 11 rebounds for the Spurs. Tony Parker had 19 points and eight assists, but shot just 6 of 23 from the field. The Spurs had one final chance down 103-100, but Chris Bosh blocked Danny Green's 3-pointer from the corner as time expired. Bosh had said Green wouldn't get open the way he has all series — and he didn't.