Iran´s chief nuclear negotiator said Iran wouldn´t compromise on its right to enrich uranium, casting doubts on whether the country could reach a deal during talks with international powers in Moscow this month.

Saeed Jalili, the negotiator, updated lawmakers in Iran´s parliament on Wednesday over the status of the country´s nuclear talks, in a speech that was aired live on radio and published by official media.

Mr. Jalili´s narrative of several rounds of nuclear talks dating to last year suggested a hardening of Iran´s position. The diplomat, who represents the views of Supreme Leader Ayatollah Ali Khamenei, dismissed a suspension of uranium enrichment, a central demand of the international powers.

The diplomat said Iran had recently threatened to pull out of the talks if they only focus on the nuclear issue and don´t address Iran´s other concerns such as human rights in Bahrain and piracy in the Persian Gulf.

He said Tehran only changed its mind after Catherine Ashton, the European Union´s Foreign Secretary, called him Monday to reassure him Iran´s concerns were on the table.

Mr. Jalili also suggested the West was conducting a colonial war against Iran to keep it from scientific advancement. "The Islamic Republic´s nuclear program and nuclear energy is based on our legitimate rights and it´s a symbol of our resistance and progress," he told parliament.

He added that the West´s opposition to Iran´s nuclear program stemmed from "fear that the Islamic Republic could serve as a role model for progress and defiance in other countries."

Iran is scheduled to resume talks with the five permanent United Nations Security Council members and Germany in Moscow on Monday and Tuesday. The meetings will mark the third round of negotiations this year after two others in Istanbul in April and Baghdad in May.

Amid high expectations, those talks were ultimately regarded as unproductive and both Iran and the international community only agreed to keep negotiating.

The talks come ahead of plans by the EU to impose a full embargo on Iranian oil exports on July 1 and amid suggestions by Israel that it could conduct a military strike against Iran´s nuclear program if diplomacy fails.

Japan, looking to secure a steady energy supply, is pressing the EU to loosen its pending sanctions, which would prohibit European firms from insuring Japan´s imports of Iranian oil after July 1, said people familiar with the effort.

The EU´s views on the state of talks with Iran appear to be divided. Some EU diplomats say the coming talks risked collapse, while others said talks would likely continue for some time.

"It´s not about a breakthrough or no breakthrough, it´s about the level of serious engagement which will lead eventually to a breakthrough," said a senior diplomat. "We are very much determined to pursue this process as long as there is momentum to pursue it and as long as there is commitment [from Iran] to pursue the nuclear issue in substance."

Russian´s Foreign Minister Sergei Lavrov traveled to Tehran on Wednesday to discuss the coming talks, as well as other regional issues such as Syria, meeting with his counterpart Ali Akbar Salehi.

Mr. Lavrov didn´t give details of his meetings but said the "Iranian side is interested in coming up with solutions" to settle the standoff.

Russia and China are seen as the most sympathetic countries toward Iran among the Security Council members.

The six-nation negotiating group says it is concerned that Iran is developing nuclear weapons and has demanded that Iran suspend its current practice of enriching uranium to 20% purity. Nuclear weapons require an approximate 90% enrichment level, but nuclear experts say the most extensive technical work is required in the earlier stages— moving to 20% purity from 3.5% levels.

Iran insists that the intention of its nuclear program is for obtaining peaceful energy and medical advancements. Iran had indicated that it might consider reducing enriched uranium to below 5% if the international community would ease the economic sanctions that are crippling its economy.

But Western countries say they won´t lift sanctions now and worry that Iran might be stalling talks to buy time for its nuclear program.

—Laurence Norman in Brussels and David Crawford in Berlin contributed to this article. (Copyright © Dow Jones & Company, Inc.) 06/14/12)