James Stewart has taken his first AMA Supercross victory as a Yamaha rider after narrowly holding off defending champion Chad Reed during round two at Phoenix.

Stewart, who failed to finish at Anaheim after missing a gear in a corner and being hit by Reed and then Kevin Windham, took the lead from surprise A1 winner Josh Grant on the opening lap of the main event.

Suzuki rider Reed then got by Grant on the third lap and set after Stewart in what proved to be a thrilling final, with just half a second separating the former and present AMA Supercross champion at the end of 20 laps.

"My goal was to try to win the race and I was able to do that, so it was good," said Stewart. "I just wanted to ride better than I did last week.

"It is nerve-wracking but at the same time, I just had to be composed and ride in my own head," he commented regarding his close duel with Reed. "That's the only way I can get it done. Obviously he was riding good; he had better parts than I did, and I had better parts than he did. The crowd was going wild and I knew when he would get close.

"The championship is definitely not going to be given to me and I know I have to work for it. After last weekend, having the bobble that I had, I don't think it was anybody's fault, but I do think I put myself in a small hole and I have to dig myself out."

"I felt real good tonight,," said Reed. "I was chasing the #7 bike down and having fun but it wasn't enough. I will take the championship week by week and stay on the podium."

Reed has moved to within three points of surprise championship leader Grant, who finished third at Phoenix for Joe Gibbs Yamaha. Stewart sits seventh in the championship, 18 points behind Grant. Multiple Lites champion Ryan Villopoto was seventh in his second 450cc AMA start.

In the Western Region Supercross Lites event, Ryan Dungey took the title lead with victory in the main event.

The Rockstar Makita Suzuki's rider took the lead on lap six at Chase Field Stadium - packed out with more than 46,000 fans - when leader Jake Weimer (Kawasaki) crashed. Dungey now holds a two-point lead over Weimer in the series.

"After I saw Jake crash, I knew there were plenty of laps left so I needed to be smart and consistent. I'm happy to move into the points lead as we head back to Anaheim next weekend," said Dungey.

KTM's Justin Brayton was second and Kawasaki's Ryan Morais third. Weimer recovered to fourth.