WASHINGTON, Dec 4 (Reuters) - Iran walked back any compromises it made in previous talks on reviving the 2015 nuclear deal, pocketed all compromises made by others and asked for more during indirect U.S.-Iranian talks this week, a senior State Department official said on Saturday. Iran continues to accelerate its nuclear program in provocative ways and China and Russia were taken aback at how far Iran had walked back its proposals in last week"s talks in Vienna, the official told reporters on condition of anonymity. The indirect U.S.-Iranian talks on saving the 2015 Iran nuclear deal broke off on Friday as European officials voiced dismay on at sweeping demands by Iran"s new, hardline government. The seventh round of talks in Vienna is the first with delegates sent by Iran"s anti-Western President Ebrahim Raisi on how to resuscitate the agreement under which Iran limited its nuclear program in return for relief from economic sanctions. Iran came "with proposals that walked back anything - any of the compromises Iran had floated here in the six rounds of talks, pocket all of the compromises that others, and the U.S. in particular, had made, and then asked for more," the senior U.S. official said. The U.S. official told reporters he did not know when the next round of talks would resume - other officials had said they would reconvene next week - and he stressed the date was less important than Iran"s willingness to negotiate seriously.