SANTA CLARA, United States (AFP) - Michael Phelps, the 18-time Olympic champion and 22-time medal winner who came out of retirement in April, continues his comeback next week at the Santa Clara Grand Prix.

USA Swimming announced Phelps was entered for the four-day meet that begins June 19 but did not detail which events he might swim.

The meet is a key warm-up event for the US national championships on Aug 6 to Aug 10 at Irvine, California.

That is the American qualifying meet for next year's world championships in Russia, which is the last major global swim showdown ahead of the 2016 Rio de Janeiro Olympics.

While Phelps has not confirmed that he is aiming to swim at another Olympics, he and coach Bob Bowman have usually kept tight-lipped about plans even ahead of Phelps' run to a record eight gold medals at the 2008 Beijing Olympics.

Phelps won the 100 butterfly title last month at Charlotte, North Carolina, in his first final since the London Olympics.

He finished second to Olympian Ryan Lochte in the same event at the final two months ago in Mesa, Arizona, in his first meet since the 2012 London Games.