US President Donald Trump on Wednesday reignited a feud with the father of one of the three UCLA basketball players who were detained in China on suspicion of shoplifting, calling him an ?ungrateful fool? in a series of early-morning tweets.

LaVar Ball, the father of LiAngelo Ball, has played down Trump?s involvement in the three athletes? release from Chinese detention after they admitted to stealing items from three stores during a team trip to China earlier this month.

?...LaVar, you could have spent the next 5 to 10 years during Thanksgiving with your son in China, but no NBA contract to support you. But remember LaVar, shoplifting is NOT a little thing. It?s a really big deal, especially in China. Ungrateful fool!,? Trump tweeted.

In another tweet, Trump took sole credit for getting LiAngelo Ball out of a long-term prison sentence - and not the White House, the State Department or LaVar Ball?s associates in China.

?IT WAS ME. Too bad! LaVar is just a poor man?s version of Don King, but without the hair. Just think.. ,? Trump tweeted, referring to the American boxing promoter.

Ball has declined to thank the president and downplayed his role in helping to get his son home from China.

The three players have apologised and thanked Trump for helping secure their release by raising the issue with Chinese President Xi Jinping during a visit to the country earlier this month. All three players have been suspended indefinitely from the UCLA basketball team.

On Sunday, Trump tweeted that he ?should have left them in jail!?

The Republican president also weighed in on another pet peeve: National Football League players kneeling during the national anthem at games. The Washington Post reported on Tuesday that league owners are considering reverting to an earlier practise of keeping players off the field during the national anthem.

?The NFL is now thinking about a new idea - keeping teams in the Locker Room during the National Anthem next season. That?s almost as bad as kneeling!? Trump said in a third early-morning tweet. ?When will the highly paid Commissioner finally get tough and smart? This issue is killing your league! ...?

A NFL representative had no immediate comment.