Iran’s actions represent a serious threat to the national security of the United States and to the American troops that have been deployed abroad, they said. As well, the American interests and allies are endangered.

Trump has been eager to curb the Iran threat. He has given Europe an ultimatum to fix the nuclear deal, or he will pull the United States out of it.

The senators encouraged Trump to keep pressuring Iran. “As many serious and urgent threats compete for attention, we believe it is important to remain focused on the growing threat that Iran’s ballistic missile program represents. We applaud your administration’s recent actions with respect to Iran’s ballistic missile program. We are eager to work with the administration to take additional steps to better protect the United States and our allies against this threat.”

The Iranian regime violates the human rights of the people of Iran and it plunders the nation’s wealth on terrorism and proxy groups and militias, wrote the senators, who also said that the Iranian regime’s support for the Syrian dictator Bashar al Assad’s regime is unacceptable. “As the world’s worst state sponsor of terrorism, Iran actively supports terrorist groups like Hezbollah and props up the murderous Assad regime that uses gas to slaughter the Syrian people.”

They stated that they support the administration’s decision to sanction five Iranian entities that support Iran’s ballistic missile program, but urged it to further use the authorities under Executive Order 13382 to designate “all remaining agents, affiliates, and subsidiaries associated with the designated entities and their parent companies.”

They advised that more “robust” sanctions be imposed. “This includes designating or otherwise sanctioning the foreign and domestic supply chains associated with Iran’s ballistic missile programs. We encourage the administration to work with allies and partners to make these sanctions multilateral where possible.”

Because the Islamic Revolutionary Guard Corps (IRGC) has control over Iran’s ballistic missile inventory and the IRGC’s Aerospace Force (IRGC-AF) manages the upkeep, testing, maintenance and transfer of weapons, the senators point out that it is therefore necessary that anyone providing assistance should also be sanctioned. “This material support can be as high-tech as those engaged in warhead engineering for Iran’s missiles, or as low-tech as fixing the transporter-erector launchers (TELs) that provide Iran’s missile force with mobility.”

The letter was also signed by Tom Cotton (R-Ark.), John Cornyn (R-Texas), Ted Cruz (R-Texas), James Inhofe (R-Okla.), Cory Gardner (R-Colo.), Steve Daines (R-Mont.), John Barrasso (R-Wyo.), Shelley Moore Capito (R-W.Va.), Dean Heller (R-Nev.), David Perdue (R-Ga.), Johnny Isakson (R-Ga.) and James Risch (R-Idaho).