British Foreign Minister William Hague (L). shakes hands with Iran's Foreign Minister Mohammad Javad Zarif at the beginning of their bilateral meeting at the United Nations in New York September 23, 2013. REUTERS/Jason DeCrow/Pool

DUBAI (Reuters) - A meeting between Iran's top diplomats and world powers at the United Nations this week will start a "new era" in efforts to end a dispute with the West over Tehran's disputed nuclear program, the Iranian Foreign Ministry said on Tuesday.

It did not hint at any concessions that could draw further criticism from hardline groups who have voiced their concerns over signs of a possible rapprochement with the United States.

The European Union said on Monday that Iranian Foreign Minister Javad Zarif would meet the representatives of Britain, France, China, Russia, the United States and Germany to discuss the Iranian nuclear program.

The meeting, due on Thursday and expected to include U.S. Secretary of State John Kerry, would be the highest-level encounter between Washington and Tehran since relations were cut in 1980 at the height of the U.S. embassy hostage crisis.

"These talks are the start of a new era. The Islamic Republic has explicitly stated its views regarding its rights to peaceful nuclear energy and the right to enrich (uranium) on Iranian territory," Foreign Ministry spokeswoman Marzieh Afkham told a news conference, Mehr news agency reported.

"This meeting represents a serious commitment of the foreign parties to reach a solution based on a specified timeframe."

Before leaving for New York on Monday, newly elected president Hassan Rouhani said he wanted to present Iran's "true face" and to pursue talks and cooperation with the West to end the nuclear dispute.

PEACEFUL PURPOSES

Iran says it is enriching uranium only to fuel a planned network of nuclear power stations, and for medical purposes.

The United States and its allies have imposed tough economic sanctions on Iran over suspicions that it is seeking a nuclear weapons capability.

Refined uranium can provide the fissile material for nuclear bombs if processed further, which the West fears may be Tehran's ultimate goal given that it has a history of hiding some nuclear activity from U.N. anti-proliferation inspectors.

U.S. officials have also said a meeting is possible this week between President Barack Obama and Rouhani, who were both due to address the General Assembly on Tuesday.

But on Tuesday, Afkham appeared to play down this possibility, telling reporters: "No program has been organized for a meeting and it is rather (a) discussion in the media."

Iran's leader, Ayatollah Ali Khamenei, appears to have endorsed Rouhani's diplomatic initiative but there are rumblings of discontent within hardline constituencies, especially the military, over the signs of detente.

"Those whose hearts are fixed on America - either they don't know America or they don't know politics," said Massoud Jazayeri, deputy chief of the Iranian armed forces, according to the Fars news agency.

"Freezing Iranian assets, downing an Iranian passenger plane, sanctions, espionage and terrorism are only part of America's dark file in its relations with the Islamic Republic."

(Reporting by Marcus George, Editing by William Maclean and Kevin Liffey)