Elon Musk has said he is planning to pledge about $45 million a month to a newly formed super PAC backing former President Donald Trump's White House bid, the Wall Street Journal reported Monday, citing people familiar with the matter.

Musk had not given any money to that group, called America PAC, as of the end of June, according to a quarterly financial filing submitted to the Federal Election Commission on Monday evening.

It is unclear if he has donated in July. Emails to Musk's associates were not immediately returned late Monday.

But the super PAC, which was formed in late May, has received contributions from other high-profile entrepreneurs, including Palantir co-founder Joe Lonsdale and crypto billionaires Cameron and Tyler Winklevoss, the filing showed.

Lonsdale donated $1 million to America PAC through Lonsdale Enterprises, an entity linked to the eponymous tech investor, multiple outlets reported.

The Winklevoss twins each donated $250,000 to the super PAC, the FEC filing showed.

Lonsdale could not immediately be reached for comment.

America PAC brought in $8.8 million and spent $7.8 million between its inception and the end of June, leaving it with just under $1 million in cash on hand, according to the FEC filing.

Musk, the CEO of Tesla and SpaceX and one of the world's richest people, officially endorsed Trump on Saturday, minutes after the Republican presidential nominee survived an assassination attempt at a campaign rally.

The report of Musk's pledge to help Trump defeat President Joe Biden came on the first day of the Republican National Convention in Milwaukee, where Trump secured enough delegates to officially become the GOP nominee.

Read the full report from The Wall Street Journal.

— CNBC's Lora Kolodny contributed to this report.