Former Speaker of the House Newt Gingrich officially placed his support Wednesday behind presumptive Republican presidential nominee Donald Trump.

"I endorse Donald Trump," he told Fox News' Sean Hannity in an interview Wednesday night on "Hannity." "I am going to work very hard for the nominee."

Gingrich said he didn't get involved in the race earlier because he had "very good friends."

"John Kasich is a great personal friend of mine,  Ted Cruz ran a great campaign," he told Hannity. "I tried to be an objective observer."

Gingrich is the second high-profile endorsement Trump received on Wednesday.

Earlier in the day, T. Boone Pickens, a billionaire oil investor, said it's time to "try somebody different" as the GOP presidential nominee, whose unorthodox bid has given other major GOP donors pause.

Pickens made the comments at the SALT conference, an annual gathering of financial industry leaders held in Las Vegas.

Pickens, one of the party's most prolific donors, said Trump called him on Monday and the two had a chuckle about how he'd given big money to GOP rivals Jeb Bush and Carly Fiorina before Trump beat them.

Pickens says he told Trump he's with him now and would contribute to Trump and likely to a pro-Trump super PAC, as well, although he says is too early to put a dollar amount on it.

The Associated Press contributed to this report.