NEW YORK (AFP) - President Donald Trump is about to become a grandfather for the ninth time after his son Eric revealed on Monday (March 21) that he and wife Lara are expecting their first child.

"@LaraLeaTrump & I are excited to announce that we are adding a boy to #TeamTrump in September," Eric Trump tweeted.

The president sent congratulations in a retweet. "Very proud and happy for the two of you!" he wrote.

Donald Trump already has eight grandchildren: his oldest son Donald Jr., 39, has five kids, while his daughter Ivanka, 35, has three.

Eric, Ivanka and Donald Jr. are the children of Trump's first marriage to Ivana Trump.

Eric and his older brother have run their father's firm, the Trump Organization, since the Donald Trump's arrival in the White House in January.

The company oversees the president's vast array of investments in the United States and abroad, from real estate to hotels and golf clubs.

Eric's wife Lara Trump, a 34-year-old former producer for the tabloid television news show "Inside Edition," is now involved with animal charities.