Galen Rupp competes during the men’s 10,000 meters at the US championships on Thursday in Eugene, Oregon. Photo: AFP

Galen Rupp capped a month of turmoil with a seventh straight US national title in the 10,000 ­meters on Thursday in Eugene, Oregon, punching his ­athletics World Championships ticket amid ­doping accusations."It's been hard I'm not ­going to lie," Rupp said of the ­allegations leveled in a BBC ­documentary in collaboration with the ­ProPublica website that his coach, ­Alberto Salazar, violated various anti-­doping rules and doped Rupp himself with testosterone in 2002 when Rupp was only 16.

"It has been difficult to focus," the 10,000 meters Olympic silver medalist said, adding that he was "100 percent behind" the detailed rebuttal issued by Salazar on Wednesday in which the coach said he would "never permit" doping.

"I believe in clean sport, and I think the truth will prevail," said Rupp, who broke from a tight leading group to seize the lead with three laps remaining and pulled away inexorably to win in 28 minutes 11.61 seconds at the US championships.

With Benjamin True (28:14.26) and Hassan Mead (28:16.54) trailing in his wake, Rupp gave a thumbs-up sign as he crossed the line under Salazar's watchful eye.

"It was obviously a good test," said Rupp, who received a warm reception from his home state fans in Oregon. "A good field - they made it really honest."

Rupp reiterated his support for Salazar, who also coaches ­Britain's double Olympic and world ­champion Mo Farah.

Farah hasn't been accused of wrong-doing, but he's been dogged by questions about whether he should continue to train under Salazar in Oregon.

"We've talked, for sure," Rupp said of Farah.

"I can't speak for him, ­obviously, but I think we've got a great thing going and he's had great success. We know we do things the right way so really that's all I've got to say to him."

Facing a massive scrum of journalists, Rupp said he ­intended to keep his mind on his racing through the end of the ­championships, with the 5,000 meters scheduled for Sunday.

"I'm ready to race," he said. "This is why I compete and I'm not going to let anything get in the way of that."

Among the seven finals on the opening night of the ­meeting, Marquis Dendy punched his ticket to Beijing with a victory in the men's long jump with a wind-aided leap of 8.68 meters.

Jeffrey Henderson, who owns the best jump in the world this year of 8.50, was second with 8.44 meters and Michael Hartfield was third with 8.42.

American record-holder Michelle Carter won the women's shot put with a throw of 20.02 meters ahead of Tia Brooks (18.93 meters) and Jeneva Stevens (18.84 meters).

Molly Huddle won the women's 10,000 meters in 31 minutes 39.20 seconds ahead of 2008 Olympic bronze medalist Shalane Flanagan (31:42.29) and Emily Infeld (31:42.60).