Launched in 1997 as a postal DVD rental business, Netflix has grown to become the world's largest subscription streaming service. The deal, the biggest the film industry has seen in a long time, would cement its number one position.
Under the agreement several global entertainment franchises, such as Looney Tunes, The Matrix and Lord of the Rings, would move to Netflix.
The deal is expected to be completed after Warner Bros splits its business in the second half of 2026.
The US Justice Department's competition division, which oversees major mergers, could contend that the deal violates the law if the combined businesses account for too much of the streaming market.
At an event at the John F Kennedy Center in the US capital, Trump said that Netflix has a "very big market share" which would "go up by a lot" if the deal goes ahead.
Trump added he would be personally involved in the decision on whether or not to approve the deal and repeatedly highlighted the size of Netflix's market share.
He also said that Netflix's co-CEO Ted Sarandos recently visited the Oval Office and praised him for his work at the company.
"I have a lot of respect for him. He's a great person," said Trump. "He's done one of the greatest jobs in the history of movies."
Mr Sarandos earlier acknowledged that the agreement may have surprised investors but said it was a chance to position Netflix for success in the "decades to come".