TEHRAN - World powers were on Thursday studying Tehran's new nuclear proposals as a top Iranian official insisted there will be no let-up in the Islamic republic's controversial uranium enrichment programme.

Iranian foreign minister Manouchehr Mottaki on Wednesday delivered to representatives of six world powers in Tehran an updated package of proposals aimed at resolving an impasse over Iran's nuclear drive.

The package was given to envoys of the United States, Britain, France, Russia, China and Germany -- six powers involved in efforts to convince Tehran to halt sensitive nuclear work which they suspect is to make an atomic bomb.

Tehran says its nuclear programme is entirely for peaceful purposes and that it is entitled to pursue it, as a signatory to the Non-Proliferation Treaty.

On Thursday, Russia and China said they were evaluating Iran's latest package, details of which have yet to be made public.

"It contains a lot of arguments which require expert evaluations," Russian foreign ministry spokesman Andrei Nesterenko said.

"After studying this document and exchanging opinions with our partners in the six-party talks, there will be found an understanding as to how to evaluate the document that we've received," Nesterenko added.

China too said it was studying the document put forward by Iran and called on all parties to step up efforts to resolve the issue.

"We believe that under the current circumstances, relevant parties should step up diplomatic efforts and resume talks as soon as possible to seek a comprehensive, long-term and proper settlement of the issue," foreign ministry spokeswoman Jiang Yu told journalists.

Britain, whose relations with Iran have deteriorated since the disputed re-election of President Mahmoud Ahmadinejad on June 12, said it was "committed to a meaningful dialogue" to address concerns over Tehran's atomic drive.

"Our offer of talks on the nuclear issue (made in April 2009) still stands, and we hope that Iran will respond to this as soon as possible," a Foreign and Commonwealth Office spokeswoman said in London.

Iran has accused Britain of having a role in the post-election unrest in Tehran which officials say killed about 36 people.

According to the Iranian media on Thursday, Iran's envoy to the International Atomic Energy Agency (IAEA) again insisted at the agency's meeting in Vienna that Tehran will continue enriching uranium, which lies at the center of the nuclear controversy.

Ali Asghar Soltanieh told IAEA governors that it is Iran's policy "not to have suspension (of uranium enrichment) and to fully go ahead with our undeniable right of using peaceful nuclear technology," the conservative Jomhuri Eslami reported.

World powers have given Tehran a late September deadline to begin negotiations with them concerning the atomic programme or face more sanctions. Tehran is already under three sets of UN sanctions.

Talks with Tehran gained significance after US President Barack Obama, soon after his January inauguration, made diplomatic overtures with Iran to resolve several outstanding issues, including the nuclear crisis.

Washington and Tehran have had no diplomatic relations since the 1979 Islamic revolution in Iran which toppled the US-backed shah.

Mottaki told representatives of the six world powers on Wednesday that Tehran was "ready to discuss political, security, economic, cultural and international issues with the other parties, on the basis of respect for the sovereignty and rights of nations, and without pressure and threats."