Allyson Felix fails to hand over the baton to English Gardner during the preliminary heats of the 4×100 relay on Thursday. (Dylan Martinez/Reuters)

RIO DE JANEIRO — The United States’ women’s 4×100-meter relay team dropped the baton in Thursday’s first-round heat, the Americans’ hopes of defending their Olympic title apparently dashed.

But after arguing that sprinter Allyson Felix was impeded during a handoff to English Gardner, the Americans filed a successful protest and will be given a second chance to qualify for the final.

The Americans will have a chance to rerun the track Thursday evening and post a time that could give them a spot in the final field.

Canada finished one-hundredth of a second faster than China, meaning the United States would bump the Chinese from the final if it posts a better qualifying time.

“I got bumped coming into the exchange zone and it just completely threw me off balance,” Felix said. “I tried to hold it together to get it to English.”

She couldn’t, though, and the baton fell to the ground. Felix picked it up and the Americans made sure to finish the race, something their coaches stressed at their pre-Olympics relays camp.

“I just remember them telling us, if there’s an appeal, you have to make an effort,” Felix said, after the race — something she had told NBC immediately after finishing.

Officials with U.S. Track and Field filed the protest after the race, saying a runner from the Brazilian team impeded Felix as the Americans tried to make their handoff.

Here’s the relevant rule:

The Brazilian team was disqualified after the race for obstruction.

“We’re just going to regroup, get ourselves together and go out there and be able to compete in the final,” Gardner before a final decision had been made.

After missing the podium in 2004 and ’08, the U.S. relay team won gold four years ago in London, edging out the speedy Jamaicans. Felix and Tianna Bartoletta are the only returners from that group. Felix, 30, is also in the relay pool for the women’s 4×400-meter race.