Biden had expressed continued support for the pact forged while he was vice president in the Obama administration, granting some sanctions relief to Iran in exchange for curbs on its nuclear program. Biden’s nominee for deputy secretary of state, Wendy Sherman, helped hammer out the Iran deal in 2015.

But it’s unclear how receptive Iran’s leadership remains to renegotiate with world powers after the President Trump pulled out. And Europe sees a tight window of opportunity following the president elect’s inauguration on Wednesday.

Iran’s presidential election in June could bring in a new government that’s more in line with hard-liners within the inner circle of the supreme leader, Ayatollah Ali Khamenei, who has the last word in all key decisions.