WASHINGTON — (CNN) Donald Trump claimed on Thursday that he had seen video of the controversial US transfer of $400 million in cash to Iran in January at the same time Tehran released four US hostages.

Republicans say the transfer amounted to a ransom payment — a charge the Obama White House strenuously denies — and are using it to bludgeon the Democratic administration.

But Trump’s decision to focus on a tape whose existence has been questioned risked diverting attention from his wider attacks on Iran policy, which have the potential to put the Obama administration and his Democratic opponent Hillary Clinton in a tough political spot.

“A tape was made — you saw that?” Trump asked the crowd sat the start of his rally in Portland, Maine. “With the airplane coming in, nice plane … and the money coming off, I guess.”

Trump went on to speculate that the tape was “given to us” by the Iranians to “embarrass our country and embarrass our president,” apparently concluding that the footage had been released by Iranian intelligence or government security services.

“We have a president who’s incompetent,” Trump said.

It remains unclear what tape Trump was referring to Thursday.

He made similar comments on Wednesday.

The Washington Post reported that the tape Trump had seen was included in a Fox News report about the $400 million transfer on Wednesday, but that the executive jet displayed appeared to be in Geneva that day, not Iran, and did not show the transfer of cash.

Trump’s spokeswoman, Hope Hicks, did not return requests for comment on the video.

The billionaire has frustrated Republicans in recent days with the lack of discipline at his campaign appearances and may have again stepped on his message by talking about a tape rather than the wider issue of why the United States was sending millions of dollars to its longtime foe.

The Obama administration has repeatedly rejected GOP accusations that the cash — part of a $1.7 billion agreement to settle a decades-old arms deal dispute — was meant to grease the release of four US prisoners who were freed in January when Tehran implemented a landmark nuclear deal.

A fifth US prisoner was released separately.

Secretary of State John Kerry insisted Thursday that the United States never pays ransoms for hostages, rejecting accusations that a $400 million payment to Iran was a quid pro quo for the release of American prisoners.

“First of all, the United States of America does not pay ransom and does not negotiate ransoms with any country,” Kerry said at a news conference in Argentina. “We never have and we’re not doing that now. It is not our policy.”

A furor erupted after The Wall Street Journal reported Wednesday on the circumstances and timing of a cash payment to Iran.

CNN had at the time reported that the transfer had been arranged.

Trump has sought to make the Iran deal — which the administration had previously announced in January — into a political plus at a rocky moment for his campaign.

“You see it, you don’t believe it,” Trump said, accusing the administration of sending “bushels and bushels of cash” to Iran.

The GOP nominee suggested the money would find its way into the pockets of officials or be diverted towards terrorism, he said.

“How stupid are we to allow us to keep on going on?” asked Trump.

Two senior US officials told CNN, however, that while there was no “ultimatum” by the Iranians forcing the US to provide the $400 million cash payment in order to free the Americans, there was a general understanding on both sides that those issues — along with the incipient nuclear deal — would get wrapped up simultaneously.

Internally, there was an interagency discussion and nobody put their foot down trying to stop it from happening, even though there was an acknowledgment that the optics were problematic.

When it became clear that all three issues were close to resolution around the same time, the decision was made to go ahead and do it all at once even so.

Republicans, including presidential nominee Donald Trump, condemned the transaction and have seized on it as a payment of ransom for prisoners that could put other Americans at risk.

They also are labeling it an example of irresponsible administration dealings with a rogue power.

“Iran was in big trouble, they had sanctions, they were dying, we took off the sanctions and made this horrible deal and now they’re a power,” Trump said Wednesday in Daytona Beach, Florida.

Asked whether the Americans would have been released without the cash payment, one official said, “it is unknowable.”

The money was flown to Iran on a plane carrying wooden pallets stacked with Swiss francs, euros and other currencies.

The payment was made with President Barack Obama’s approval as the first tranche of a $1.7 billion settlement resolving claims at an international tribunal at The Hague.

The claims related to a failed arms deal under the time of the Shah Mohammad Reza Shah Pahlavi in which the US was left with Iranian funds when he was toppled by the Islamic Revolution in 1979 and the two countries cut ties.

Kerry tried to tamp down the uproar Thursday, saying, “This is not a new story. It doesn’t represent anything the American people weren’t told by the President and by the administration.”

Obama himself is likely to face a grilling on the Iran story during a news conference at the Pentagon later on Thursday.

The Obama administration has admitted the circumstances of the payment do not look good but insists it was part of a complicated set of diplomatic maneuvers that were separate but came to fruition at the same time.

“We were aware … of the optics … (which is) one of the reasons we tried to address it up front,” said State Department spokesman Mark Toner on Wednesday.

“The President spoke to this settlement, Secretary Kerry spoke to the settlement at the time and tried to say, ‘Look, guys, I know (what) it looks like, but there’s no there there,’ ” he said.

“And so we’ve always been aware of it, but that didn’t keep us from, frankly, sealing a deal that saved the American taxpayers a considerable sum of money.”

Iran had been seeking more than $10 billion in arbitration.

Although the administration announced in January that it would pay $1.7 billion to Iran, it did not disclose the cloak-and-dagger style of the payments.

The Journal report detailing the episode on Wednesday reopened the controversy over the administration’s approach to Iran, including the nuclear deal, which Republicans vigorously oppose.

The White House argued on Wednesday that the fact Republicans are seizing on the cash story is proof that they are struggling to maintain their opposition to the historic nuclear agreement itself.

Officials also said the cash was delivered in such an unorthodox manner because Iran was still isolated from the international financial system owing to international sanctions.