* Differences narrowed but not easy to bridge, Iran says
* Iran says onus mainly on U.S. to clinch new agreement
* U.S. puts onus on Iran, 'fair distance' still to any deal
* Hardliner Raisi won Iran's presidential election
* Israel: Don't talk to 'hangmen regime' under Raisi (Adds E3 diplomats, Borell)
By Francois Murphy and Parisa Hafezi
VIENNA/DUBAI, June 20 (Reuters) - Western officials warned Tehran on Sunday that negotiations to revive its nuclear deal could not continue indefinitely, after the sides announced a break following the election of a new hardline president in Iran.
Negotiations have been ongoing in Vienna since April to work out how Iran and the United States can both return to compliance with the nuclear pact, which Washington abandoned in 2018 under then-President Donald Trump, and Iran subsequently violated.
Sunday's pause in the talks came after Ebrahim Raisi, a hardliner and fierce critic of the West, won Iran's presidential election on Friday. Two diplomats said they expected a break of around 10 days.
Raisi will take office in early August, replacing pragmatist Hassan Rouhani, under whom Tehran struck the deal agreeing to curbs to its nuclear programme in return for the lifting of international sanctions.
Iranian and Western officials alike say Raisi's rise is unlikely to alter Iran's negotiating position: Iran's hardline Supreme Leader Ayatollah Ali Khamenei already has final say on all major policy.
Still, some Iranian officials have suggested that Tehran could have an interest in pushing through an agreement before the new president takes office in August, to give Raisi a clean slate.
An Iranian government official close to the talks told Reuters that if a deal is finalised before Raisi takes office, the new president will be able to deflect blame for any concessions onto his predecessor: "Rouhani, not Raisi, will be blamed for any future problems regarding the deal," he said.
Britain, France and Germany, the European "E3", have effectively been acting as mediators, shuttling between the Iranian delegation and a U.S. team that - Washington having quit the pact - is not a formal participant.
The Western countries say the longer Iran violates the deal and produces banned nuclear material, the harder it becomes to restore the pact.
"As we have stated before, time is on nobody’s side. These talks cannot be open ended," E3 diplomats said in a note sent to reporters, adding that the most difficult issues still need to be resolved.