Iran's top decision-maker Ayatollah Ali Khamenei said on Monday that while he is not against a resumption of nuclear negotiations with the world's major powers, the talks will "lead nowhere".
"Some of the officials of the previous government as well as the officials of this government think the problem will be resolved if they negotiate the nuclear issue," Khamenei said in remarks published on his website Khamenei.ir.
"I repeat it again that I am not optimistic about the negotiations and they will lead nowhere, but I am not against them," he added.
Iran is due to resume talks on Tuesday in Vienna with the P5+1 powers -- Britain, France, the United States, Russia and China plus Germany -- aimed at reaching a comprehensive accord on its controversial nuclear programme.
Under a landmark interim deal clinched in November, Iran agreed to freeze some nuclear activities for six months in exchange for modest sanctions relief and a promise by Western powers not to impose new restrictions on its hard-hit economy.
Western powers and Israel have long suspected Iran is pursuing a nuclear weapons capability alongside its civilian programme, charges denied by Tehran.
Khamenei said Iran would abide by its pledge to pursue the negotiations, adding that Iranian officials should "continue their efforts".
"The work that has been started by the foreign ministry will continue and Iran will not violate its commitment, but I repeat it again, it will lead to nowhere," Khamenei said.
"The Iranian nation emphasised that it will never succumb to the bullying and blackmailing of America," said Khamenei, referring to anti-US slogans chanted by huge crowds during nationwide celebrations last week of the 35th anniversary of country's Islamic revolution.
He also said Iran's nuclear issue was an excuse for Washington to pursue hostile policies towards the Islamic republic.
"The nuclear issue is an excuse for America (to continue) its animosity. Now, the American spokesmen are bringing up the issues of human rights and missiles."
Wendy Sherman, the US lead negotiator in the talks, said Iran should also address the concerns of the international community over its ballistic missile programme in any comprehensive deal.
US officials have also said pressure should be maintained on Iran over its alleged violation of human rights.
Iran has rejected the US allegations as "worthless" and insists its missile programme is not up for discussion.
Iranian Foreign Minister Mohammad Javad Zarif, who is leading Tehran's negotiating team, arrived in Vienna on Monday. He is scheduled to meet EU foreign policy chief Catherine Ashton over a working dinner.
Iranian media reported the negotiations would officially begin at 0830 GMT on Tuesday.