Michael Phelps' Olympic comeback gained more steam as he won his second race in as many days at the US Winter Nationals.

The 18-time Olympic gold medalist clocked 51.38 seconds on Friday to win the 100 meter butterfly at the event in Seattle, Washington.

On Thursday, Phelps won the 200 meter individual medley in a time 1.69 seconds faster than at a meet in Minneapolis three weeks ago.

"I am happy. It is really just trying to swim the fastest time I can .... I think it is a good sign," Phelps said.

In other events, Missy Franklin beat Natalie Coughlin in their first 100 meter backstroke final duel since the 2012 Olympic trials.

Franklin won in 1:00.03, while the 33-year-old Coughlin finished fourth in 1:00.41.

Phelps, Franklin and Coughlin are among the Olympic champions at the meet, which continues Saturday.

More than 40 US national team swimmers are among about 700 set to compete, but most eyes are on Phelps, who was named US Swimming's male athlete of the year despite not competing at the World Championships in Russia.

A second drunk-driving arrest in 2014 led to Phelps being removed from the US world team, leaving him to swim at the US nationals in Texas. There, he won the 100 and 200 butterfly crowns with the fastest times in the world this year and also took the 200 individual medley.
Source: AFP