EUGENE, Ore. (AP) — The leader of USA Track and Field says his visits to Brazil have made clear that "logistics will be a problem" for the more than 120 Americans who will compete at Olympic Stadium in Rio next month.

At a news conference Tuesday, USATF CEO Max Siegel called moving athletes across town from their living quarters and training centers to the stadium is one of the federation's biggest concerns and something it doesn't have full control over.

He says USATF is coordinating with the U.S. Olympic Committee to come up with contingencies for bad traffic and other transport issues.

Aretha Thurmond, a four-time Olympian who now serves as director of international teams for USATF, said staff will be in place by late July to start making test trips across the city. The Olympic track meet starts Aug. 12.

Competition at the U.S. Olympic trials resumes today at Eugene, Oregon, after a day's break on Tuesday.