President Donald Trump says he’ll make an “historic” investment in the military, but it’s unclear how that will happen without delicate spending negotiations with Congress, and maybe even his own pick to lead the Office of Management and Budget, Mick Mulvaney, a South Carolina Republican whose reputation is first and foremost as a deficit hawk.

Fresh off a weekend at his Mar-a-Lago resort in Palm Beach, Fla., Trump made his way to the Gulf Coast to address troops at U.S. Central Command and U.S. Special Operations Command headquarters in Tampa.

About Tampa’s MacDill Air Force Base, Trump vowed to “load it up” with “new” aircraft and other combat equipment — but, notably, he did not explain how he would pay for it or deal with existing defense spending limits.

The new commander in chief’s pledge to boost annual Pentagon spending to fund a buying spree of pricey new military hardware would require an increase in or termination of defense budget caps put in place by the 2011 Budget Control Act.

To do so, he would likely have to agree to also increase domestic spending to secure Democratic votes. That would be in keeping with the ways the budget caps were lifted under former President Barack Obama.

[Hawkish Trump on Iran: ‘Nothing’s Off the Table’]

Then there’s Mulvaney. At his confirmation hearing on Jan. 24 before the Senate Homeland Security and Governmental Affairs Committee, Sen. John McCain laid into Mulvaney for being insufficiently enthusiastic about more money for the Defense Department.

“All I can say to you sir is, I’m deeply concerned about your lack of support for the military,” McCain, who chairs the Armed Services committee, said.

First elected in 2010, Mulvaney has generally voted against boosts to the Pentagon’s spending that aren’t accompanied by cuts to domestic spending. He has also knocked the use of war funding to pay for everyday military expenses as a gimmick circumvents budget caps.

At any rate, the president also vowed to personally reduce the “waste” in the Pentagon budget, a perennial vow that usually amounts to very little.

And in a cryptic line near the end of his remarks, Trump declared “we are ready to fight,” an echo of White House pronouncements last week to Iran that the country was being put “on notice.”

Last week, he declined to take military force off the table as his administration calibrates its stance toward Iran — despite a campaign pledge to disentangle the United States from years of warfare in the Middle East.

Meanwhile, the president broke with his campaign rhetoric on Monday when he said he was committed to NATO, a military alliance he once called “obsolete.”

A day after he spoke by telephone with NATO Secretary General Jens Stoltenberg on Sunday, the president said “we strongly support NATO.”

“We have your back, every hour, every day, now, and always,” he added.

But in a repeat of a campaign trail message the White House said he delivered personally to Stoltenberg, Trump said, “We only ask that all of the NATO members make their full and proper financial contributions to the NATO alliance, which many of them have not been doing.”

[Trump’s Iran Sanctions Mirror Obama’s]

Trump’s positioning on NATO will be a major topic when he huddles with alliance leaders in Europe in May.