Iran’s top nuclear negotiator on Friday welcomed the return of leading world powers to talks over the country’s disputed atomic program, but urged them “not to repeat their past mistakes,” AFP reports.

Talks stalled in June when Iran rejected a proposal to suspend part of its nuclear program, asking for more substantial relief from sanctions.

Saeed Jalili, the secretary of Iran’s Supreme National Security Council, said Friday that Iran had invited world powers to resolve the impasse six months ago, which had now been considered.

“There was a six-month delay but they recently announced they are ready to come back for talks,” he told journalists at the Iranian embassy during a trip to New Delhi, according to AFP.

“We welcome their return to the talks. We hope that they will come to the talks with a constructive approach and (that) they will not repeat their past mistakes,” he added, without elaborating.

The last round of talks between Iran and the so-called P5+1 powers — the United States, Russia, China, France, Germany and Britain — yielded no breakthrough in Moscow in June.

In late November the six powers engaging Iran over its nuclear program said they were willing to hold a new round of negotiations with Tehran.

In September, Jalili met with European Union foreign affairs chief Catherine Ashton, the top negotiator with Iran over its nuclear program, but talks did not resume following that meeting. Ashton later urged Iran to take action to allay mounting international concerns over its nuclear drive.

The New York Times reported in October that Iran offered a “nine-step plan” to defuse tensions over its unsupervised nuclear program, but the compromise offer was rejected by the United States.

American officials reported said the proposal required too much from the West, including a complete end to sanctions.

Jalili later dismissed the New York Times report as “baseless.”