Donald Trump's decision to forgive his campaign loans comes on the heels of a bad fundraising month. (John Locher/AP)

Presumptive Republican presidential nominee Donald Trump's campaign announced Thursday that he has forgiven more than $50 million in loans he made to finance his presidential bid, converting them into contributions in an effort to reassure GOP donors that he is personally invested in the effort.

Trump's move comes as his aides and Republican Party officials have scrambled to demonstrate that fundraising has picked up since May, when the real estate developer received just $3.1 million in donations and ended the month with less than $1.3 million in the bank.

By turning the loans into donations, Trump's campaign cannot repay the candidate, even if a surplus arises.  The campaign, however, can continue to reimburse Trump's companies, and those of his children, for campaign-related expenses, including travel.

And while individuals are limited to giving $2,700 per election to a campaign committee, a candidate can give unlimited sums to finance his or her own bid.

Since Trump sent an email Tuesday asking supporters to contribute online, more than $6 million has come in, finance chairman Steve Mnuchin told CNBC. Separately, a high-dollar fundraiser held Tuesday night in New York in conjunction with the Republican National Committee brought in more than $6 million, according to people familiar with the figures.

"After self-funding his primary election, Mr. Trump and the campaign have assembled an exceptional fundraising operation, which in recent days has been overwhelmed with contributions for the Republican Party," the campaign said in a statement Thursday.

But many stalwart party financiers have balked at writing him a check, noting that Trump bashed wealthy donors throughout the GOP primaries and touted that he was self-funding his campaign. Most of Trump's money to his bid came in the form of loans — $45.7 million through the end of May. That spurred worries in the donor class that he would simply use money they gave to pay himself back.

Trump's decision to convert his loans into donations will likely assuage those fears, and the act represents a substantial financial commitment for the billionaire, who is famously careful with his money. It is unclear how much more he could give his campaign, if necessary. In May, Trump quipped that to self-fund the general election, he'd have to "sell a couple of buildings."