House Republicans are doubling down against the White House in a campaign to prevent Iran from doing business in U.S. dollars, the latest political spat between them and the Obama administration over implementation of the Iran nuclear deal.

House Foreign Affairs Committee Chairman Ed Royce (R-Calif.) introduced a measure this week to make denying Iran access to dollars a hard-and-fast law, while GOP leaders have issued near-daily condemnations of the administration for not promising more forcefully that Iran won’t find a backdoor to the U.S.-based financial system.

“If President Obama won’t rule out new concessions to the Iranian regime, Congress should,” Royce said. “Iran’s supreme leader must not be allowed to seek ‘death to America’ with U.S. dollars in his pocket.”

It’s a charge administration officials reject and have repeatedly tried to discredit, saying they have no intention of letting Iran start to deal in dollars.

But on Thursday, House Speaker Paul Ryan (R-Wisc.)’s office raised the pitch of the GOP’s campaign, writing on the speaker’s blog that Secretary of State John Kerry had “left the door ajar, if not completely wide open,” to giving Iran “an unprecedented economic windfall” during talks with his Iranian counterpart this week.

Ryan suggested that Friday might be the day when Kerry gives Iran the keys to the financial, dollar-denominated castle.

State Department spokesman John Kirby said on Thursday that Kerry would speak with Iranian Foreign Minister Mohammad Zarif about sanctions relief, and that the U.S. government had been trying to explain to international banks that deal in dollars where they could interact with Iran without running afoul of U.S. sanctions.

Seeking to put a lid on the tempest, administration officials have been insisting that Iran will not get access to U.S. dollars. The nuclear deal rolled back European restrictions on doing business with Iran faster than U.S. sanctions on the Islamic Republic, but Iran is finding it difficult to take advantage of those new trade partnerships because so much of the global market is dominated by U.S. dollar transactions. Many international banks fear running afoul of U.S. sanctions still in place over Iran’s non-nuclear activity.

The administration has deployed various officials to muzzle the GOP criticism, trotting out acting Treasury Undersecretary for Terrorism and Financial Crimes Adam Szubin for a speech at the Center for a New American Security last week to lay out the objectives and limitations of U.S. sanctions.

Szubin focused on the merits and dangers of being tough with secondary sanctions that govern other countries’ transactions, and have become the latest flashpoint for concern as Iran seeks to cash in on the benefits of the nuclear deal.

But Republicans — who fiercely opposed the Iran deal to begin with — aren’t satisfied.

They charge that President Obama and his deputies are primed to open the financial floodgates to Tehran, in order to satisfy Iranian leaders complaining that financial institutions’ reluctance to do business with a former pariah state has kept them from realizing the full extent of sanctions relief they were expecting under the nuclear deal.

In his speech last week, Szubin addressed said there are “risks” that come along with “tough sanctions” – and that in the long term, the U.S. could endanger its central role in global trade and finance if it made business impossible between second and third-party countries with less-stringent sanctions.

“If we lose that,” Szubin said of the U.S.’s central role in the global financial puzzle, “we lose the very economic leverage that has made our sanctions so effective in the first place.”

Democrats in Congress are taking the administration at their word that it has no intention of letting Iran access dollars.

“I haven’t seen any reason to believe there is a concern here,” Senate Foreign Relations Committee ranking member Ben Cardin (D-Md.) said Thursday. Though he opposed the nuclear deal, he stressed that his chief interest now is keeping it intact.

But congressional Republicans are skeptical, signaling they believe the administration’s explanations could just cover for a crafty sleight of financial hand instead.

“We cannot grant Iran access to the U.S. dollar in any form,” House Majority Whip Kevin McCarthy (R-Calif.) said this week. “Iran shouldn’t get relief simply because they agreed in word to a flawed nuclear deal.”