WASHINGTON — As top Republicans expressed astonishment and alarm over Donald Trump's paltry campaign fundraising totals, the presumptive nominee blamed party leaders Tuesday and threatened to rely on his personal fortune instead of helping the GOP seek the cash it needs.

New campaign finance reports showing that Trump had less than $1.3 million in the bank heading into June ignited fears that the party will not be able to afford the kind of national field effort that the entire Republican ticket depends on.

The real estate mogul responded by going on the offensive, saying GOP fundraisers have failed to rally around his campaign.

“I'm having more difficulty, frankly, with some of the people in the party,” Trump said on NBC's “Today,” adding, “They don't want to come on.”

“If it gets to a point,” he said, “what I'll do is just do what I did in the primaries,” when he lent his presidential campaign more than $43 million.

The billionaire developer increased his line of credit to the campaign by an additional $2.2 million last month — the smallest amount he has given this year — but Trump said in a statement Tuesday that “if need be, there could be unlimited cash on hand as I would put up my own money.”

If he did tap his wealth to finance his bid, it would effectively amount to abandonment of the Republican National Committee and the rest of the GOP ticket, which relies on the presidential nominee to help fund a national field organization for the fall elections.

GOP strategist and fundraiser Austin Barbour said that if Trump's fundraising does not pick up, it “could have a devastating impact” on the Republican Party.

The Trump campaign released a statement touting its fundraising as “incredible,” saying there has been “a tremendous outpouring of support” since the candidate held his first finance event May 25. Its joint fundraising committee with the RNC is expected to bring in $20 million in June, with $6 million coming from a high-dollar dinner in New York on Tuesday night, according to a person familiar with the figures.

The vast share of the money will go to the national party committee. GOP officials said the party already has nearly 500 field staffers deployed around the country and noted that the RNC has out-raised its Democratic counterpart by $46 million.

There is also growing scrutiny of his heavy use of Trump-owned companies as vendors. Of the $63 million his campaign spent through May, more than $6 million — close to 10 percent — went to pay Trump properties or reimburse Trump and his family for expenses, according to an analysis by The Washington Post. That includes $4.6 million paid to his private jet company, TAG Air, and $423,000 that went just last month to his Mar-a-Lago Club in Palm Beach, Fla.

The Trump campaign did not respond to questions about the payments.

Democratic rival Hillary Clinton ribbed Trump on Tuesday, tweeting to followers: “What is Trump spending his meager campaign resources on? Why, himself, of course.”

There's nothing illegal about the payments. Regulations do require companies— even ones owned by the candidate— to charge fair-market value.

Still, the situation has some donors spooked, said Charlie Spies, a Republican elections attorney who has worked with major contributors and was helping Trump opponent Jeb Bush.

“Why would donors give money when the first dollars go to help a billionaire buy products from his own company?” Spies asked.

Meanwhile, Clinton has been stockpiling cash. She raised more than $28 million in May and started June with $42 million in the bank.

Trump is also facing backlash for heading to Scotland to promote a golf resort later this week in the middle of one of the most tumultuous stretches of his White House bid.

“People who are serious about running for president, don't run off to Scotland where there are no votes,” said Rick Tyler, who previously advised Texas Sen. Ted Cruz's presidential campaign.

On Monday, he ousted controversial campaign manager Corey Lewandowski, who was seen as an impediment to efforts to run a more traditional operation. On Wednesday, he'll deliver a speech focused on what he describes as Clinton's “failed policies and bad judgment.”

To address his campaign's financing, Trump on Tuesday sent what he touted as his first fundraising email. (It wasn't: A joint fundraising committee he has with the RNC sent an email solicitation in his name on June 8.)

“I'm going to help make it the most successful introductory fundraising email in modern political history by personally matching every dollar that comes in WITHIN THE NEXT 48 HOURS, up to $2 million!” Trump wrote in Tuesday's missive.

Associated Press

contributed.