U.S. and Iranian officials said Tuesday an initial day of talks in Vienna on returning to the 2015 nuclear deal were “constructive,” but the Biden administration cautioned that no immediate breakthroughs were anticipated on one of the new president’s top foreign policy goals. The European-led diplomatic effort featured mediators shuttling between Iranian and American envoys, a far cry from the intensive face-to-face discussions held by U.S. and Iranian diplomats who brokered the original agreement. The goal now is agreeing on a road map toward lifting U.S. sanctions that were imposed under President Donald Trump and recommitting Tehran to its agreements under the accord, a complicated undertaking with no guarantee of success.

Still, Iran’s lead negotiator, Deputy Foreign Minister Abbas Araghchi, characterized the initial talks as on “the right track,” a notable comment given Iran’s recent tough rhetoric.

State Department spokesman Ned Price also hailed what he called progress, and acknowledged the difficulty of dismantling the network of sanctions erected after Trump puled the United States out of the agreement in 2018.

“We know there will be difficult discussions ahead but again, this is a healthy step forward,” Price said. He added that diplomatic contact, even at a remove, is the best way to fulfill Biden’s campaign pledge to comply with the original deal so long as Iran shows it is committed to doing the same.