VIENNA, Dec 9 (Reuters) - Talks on reviving the 2015 Iran nuclear deal resumed on Thursday with the United States and Israel ramping up rhetorical pressure on Tehran about the possible economic or military consequences if diplomacy fails. Iran"s top negotiator said Tehran was sticking to the stance it laid out last week, when the talks broke off with European and U.S. officials accusing Iran of making sweeping new demands and of reneging on compromises worked out earlier this year. While saying they preferred a diplomatic solution, several U.S. officials conveyed their willingness to take a tougher stance if need be. "Given the ongoing advances in Iran"s nuclear program, the president has asked his team to be prepared in the event that diplomacy fails and we must turn to other options," said White House spokesperson Jen Psaki. The indirect U.S.-Iranian talks in Vienna, in which other diplomats from the remaining parties to a now tattered 2015 deal - France, Britain, Germany, Russia and China - shuttle between them because Tehran refuses direct contact with Washington, aim to get both sides to resume full compliance with the accord. Under that accord, Iran limited its nuclear program - which the West feared would be used to develop weapons, something Tehran denies - in return for relief from U.S., European Union and U.N. sanctions. Last week"s discussions were the first after a five-month hiatus caused by the election of Iran"s new, hardline government under anti-Western President Ebrahim Raisi. Western officials have said Iran has abandoned any compromises it had made in the previous six rounds of talks, pocketed those made by others, and demanded more last week. Iran wants all sanctions imposed by the United States after then-U.S. President Donald Trump ditched the deal in 2018, to be lifted in a verifiable process. Iran began violating the deal"s nuclear restrictions about a year after the U.S. withdrawal. "Iran underlined that it is seriously continuing the talks based on its previous position," chief negotiator Ali Bagheri Kani told reporters after an opening meeting with world powers on Thursday. The United States said it would take a few days to discern whether Iran was willing to be flexible and U.S. officials hinted at the economic and military costs Iran could face if there is no diplomatic solution. Reuters exclusively reported that meetings in Washington with Israel"s visiting defences chief on Thursday were expected to include discussions about possible military exercises to prepare for a worst-case scenario to destroy Iran"s nuclear facilities should diplomacy fail. read more U.S. Defense Secretary Lloyd Austin said at the start of the meeting with his Israeli counterpart, Benny Gantz, that Iran had failed to offer constructive engagement in the Vienna nuclear talks that U.S. President Joe Biden hopes will restore the deal. Psaki focused on potential economic punishment. "If diplomacy cannot get on track soon and if Iran"s nuclear program continues to accelerate, then we will have no choice but to take additional measures to further restrict Iran"s revenue-producing sectors," she added. A senior U.S. delegation plans to visit the United Arab Emirates next week to meet banks over concerns about their compliance with U.S. sanctions designed to squeeze Iran"s economy. read more Speaking to reporters in Vienna, Enrique Mora, the European Union"s coordinator for the nuclear talks, said the sides "don"t have all the time in the world".