An influential US senator whose support of the Iran nuclear agreement helped it survive congressional scrutiny last year said he would urge the next US president to begin negotiating a “JCPOA 2.0” to address remaining concerns about Iran’s ballistic missile program and uranium enrichment capacity.

Sen. Chris Coons (D-Del.) told the Council on Foreign Relations June 23 that the Joint Comprehensive Plan of Action had been successfully implemented so far, nearly a year after it was reached. He said the next administration must make continued full implementation a top priority and that the deal’s fate would have a major impact on regional crises, US relations with Russia, NATO and European allies, and nonproliferation among Persian Gulf partners.

Coons said he was concerned that come next January, when Barack Obama leaves office, the deal “will drop from view as it largely has in this presidential campaign.”

Presumptive Democratic nominee Hillary Clinton has expressed support for the agreement, but Republican presidential nominee Donald Trump has been skeptical. Asked about Trump’s threats to renegotiate the agreement, which had the blessing of the United Nations as well as the European Union, Coons called that possibility “a fool’s errand.” (Coons spoke before the EU was shaken by Britain’s vote June 24 to exit the alliance.)