(Reuters) - World outdoor silver medalist Christian Coleman stumbled slightly in his start, then slowed before the finish, as he missed setting a world record in the 60 meters, clocking 6.46 seconds at the Boston Indoor Grand Prix on Saturday.

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The race was Coleman’s first since he ran a blazing 6.37 seconds last month, 0.02 seconds faster than the existing world record, but that time will not be ratified because electronic starting blocks were not present.

“I just wanted to come out here and execute and make sure everything is go for next week,” the young American said.

He will compete in the U.S. indoor championships/world trials next weekend in Albuquerque, New Mexico, where the rarefied air aids sprinters.

That should give Coleman an even better chance of eclipsing compatriot Maurice Greene’s 20-year-old record of 6.39 seconds.

“I’m just looking forward to the competition,” said the 21-year-old Coleman, who also has an eye on March’s IAAF world indoor championships in Birmingham, England.

Although the fast-starting American quickly pulled away from the field at Boston, he appeared to stumble a couple of steps into his race as he had in last month’s eye-catching race in Clemson, South Carolina.

While he ran all the way to the finish in last month’s race, on Saturday he backed off the final 10 meters to save himself for the national championships next weekend.

China’s Xie Zhenye finished second in 6.54 seconds with U.S. world 300 meters record holder Noah Lyles third in a personal best 6.57 seconds.

Britain’s Chris O’Hare, preparing for the Commonwealth Games in April, set a Scottish national indoor record in winning the 1,500 in 3:37.03 and Trinidad and Tobago’s Jereem Richards ran the seventh fastest 300 meters, 32.10 seconds.

Kenyan Edward Cheserek took the men’s 3,000 meters in 7:38.74 a day after running the second fastest indoor mile, 3:49.44.