Support from Congress will "strengthen" the diplomatic push to bring U.S. partners on board, according to Tillerson. He said discussions with Europeans have been ongoing for months, and he even broached the subject with Iranian Foreign Minister Mohammad Javad Zarif on the sidelines of the U.N. General Assembly last month.
The administration will push Europeans to place new sanctions on Iran in response to its ballistic missile program, Tillerson said. It will also work with partners to lay the groundwork for a complementary international deal with Iran, which would address what happens when certain provisions of the existing accord expire and how to gain access to military sites currently off-limits in Iran.
Following Trump's remarks on Friday, the heads of state of France, Germany and the U.K. said they are "concerned by the possible implications" in a joint statement. However, they said they share Trump's concerns about Iran's missile program and its "regional activities" and stand ready to take measures to address those issues, including through "constructive dialogue" with Iran.
"Our governments are committed to ensuring the JCPoA is maintained. Independent of the JCPOA, we need to make sure that our collective wider concerns are being addressed," the leaders said.
The Trump administration will also seek European sanctions on the Revolutionary Guards Corp, which is deeply embedded in the Iranian economy.
The U.S. Treasury Department sanctioned individuals and businesses tied to the Revolutionary Guards on Friday. The sanctions are based on the guards' support for terrorism, for example through funding terror groups or recruiting fighters to wage battle in places like Syria.
The administration opted against designating the Revolutionary Guards a terrorist group because doing so risks unintended consequences that could be detrimental to U.S. military actions and the administration's overall Iran strategy, according to Tillerson.