Thirteen Republican senators on Friday are pressing President Obama to detail how he plans to hold Iran accountable for any violations of international law as the nuclear deal prepares to take effect.

“We request that you provide a roadmap of what you consider to be illicit behavior from Iran, and what sanctions or punitive steps will be taken in the event of such behavior,” the senators, led by Sen. David Perdue (R-Ga.), a Senate Foreign Relations Committee member and opponent of the deal, wrote in a letter to Obama first obtained by The Hill.

{mosads}Specifically, the senators asked the president to describe what actions the Treasury Department is ready to take against individuals and entities involved in Iran’s ballistic missile program, and against foreign banks that are financing it.

Iran’s ballistic missile program was dropped from the U.S.-led negotiations with Iran over its nuclear program.

Since the deal was announced in July, Iran has conducted two ballistic missile tests in violation of international law, on Oct. 10 and Nov. 21. The administration at first prepared sanctions after the second test, but has delayed those sanctions indefinitely.

Experts suspect the White House will not do anything until after the nuclear deal — known as the Joint Comprehensive Plan of Action (JCPOA) — goes into effect, which could be as early as this weekend. Iran will receive billions in frozen assets once the deal enters effect.

“We are concerned that, despite assurances from the State Department, the sanctions delay was a reaction to Iranian President Hassan Rouhani’s move to accelerate Iran’s missile program as well as Tehran’s repeated threats to withdraw from the agreement if any new sanctions are imposed,” said the letter.

The letter, sent to the White House on Friday after a GOP retreat, is signed by Republican Sens. Kelly Ayotte (N.H.), Mark Kirk (Ill.), Bill Cassidy (La.), Thom Tillis (N.C.), John Boozman (Ark.), Ted Cruz (Texas), James Inhofe (Okla.), Johnny Isakson (Ga.), Cory Gardner (Colo.), Jerry Moran (Kan.), Orrin Hatch (Utah) and Dan Coats (Ind.).

The senators said the ballistic missile tests come in the wake of mounting Iranian aggression.

“Since the signing of the JCPOA in July, Iran has fired rockets near U.S. warships; fomented unrest in Yemen; sent weapons to the regime of Bashar al-Assad in violation of the arms embargo; taken another American hostage and refused to release the ones it presently holds; and continued its support for Hamas and Hezbollah terrorists,” it said.

Just this week, Iran detained 10 U.S. sailors overnight after their two vessels entered Iranian waters by mistake.

“In practice, it appears that your administration has allowed Iran to dictate the implementation of the nuclear deal by not taking punitive action for any of these transgressions.”

Republicans warned that failure to punish Iran for these actions could result in future violation of the Iran nuclear deal.

“We are concerned that Iran’s belligerent actions have thus far gone unpunished. As members of this body have warned before, a failure to enforce the rules is an invitation for further Iranian transgressions,” they wrote.

“If your goal is to ensure Iranian compliance with the JCPOA, it is absolutely crucial that Iran’s blatant misbehavior is met with real consequences,” they said.