James Harden and the Houston Rockets have agreed on a four-year contract extension that is reportedly the richest in NBA history.

The contract is a super-maximum extension that will guarantee Harden $US228 million through the 2022-23 season, league sources told ESPN on Sunday.

"Houston is home for me," Harden said in a statement released by the Rockets. "(Owner Leslie Alexander) has shown he is fully committed to winning and my teammates and I are going to keep putting in the work to get better and compete for the title."

Harden, runner-up for the NBA's Most Valuable Player award last season, has two years and $US59m left on his current contract.

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The four-year extension carries a value of $US169m.

Harden is coming off a career-best season in which he averaged 29.1 points, a league-best 11.2 assists and 8.1 rebounds per game.