LONDON (Reuters) - If the United States wants Iran to offer concessions that go beyond the terms of its 2015 nuclear deal, Washington must offer incentives that also exceed those in the deal, an adviser to Iranian President Hassan Rouhani said on Monday.

The comments were a rare indication from Tehran that it could discuss new concessions with Washington, although the adviser, Hesameddin Ashena, repeated Iran’s line that any talks were impossible until Washington lifted sanctions it has reimposed since withdrawing from the deal last year.

“U.S. offer for negotiations with no precondition is not acceptable while sanctions and threats continue. If they want something beyond the JCPOA (the nuclear deal), they should offer something beyond the JCPOA; with international guarantees,” he tweeted.