Donald Trump Set to Host Major Donor Gathering at Trump Tower

— -- Donald Trump will bring together a large number of campaign donors for a meeting Thursday at Trump Tower.

The first-of-its-kind meeting, first reported by the New York Times, is another step forward for Trump as he builds out his operation for the general election.

Sources within and close to the Trump campaign said the meeting would include members of Trump Victory, the joint coalition set up by the Trump campaign and the Republican National Committee.

Since becoming the GOP's presumptive nominee, Trump has begun encouraging donations, attending several organized fundraisers -- the most recent held over a week ago by longtime friend and investor Tom Barrack at his home in California.

It was after that fundraiser that Barrack threw his financial backing to Rebuilding America Now, a pro-Trump super PAC that is not sanctioned by the campaign. The Rebuilding America Now PAC plans to reserve $1.1 million in national airtime in targeted states soon, according to PAC aide Ken McKay.

"We're going to try and raise over a billion dollars, which is what's going to be necessary. The Democrats maybe will get as high as $2 billion," Trump said in an interview with NBC Nightly News last month.

ABC News' Candace Smith contributed to this report.