Khazayee said recent sanctions against Iran by the US and some European countries indicate that they are not willing to engage in meaningful dialogue for political reasons, which could lead to another standoff in talks.
Western powers negotiating with Iran over its nuclear program have not been "serious enough" in their attempts to resolve an escalating stand-off with the Islamic Republic, Khazayee said in a statement to reporters at the Iranian mission on Friday.
"It is clear for us that some members of the Group 5+1 for whatever reasons... are not forthcoming and serious enough for finding a solution," he said.
"If the talks do not proceed as it should be, we are going to have another standoff," he said. "The US and some Europeans have said they are going to increase their pressure and sanctions against us, and this... indicates that they are not willing to engage with us in a meaningful dialogue."
Iran and the sextet held two days of intensive talks in Russia's capital of Moscow on June 18-19. The two sides agreed to meet again in Early July at the level of experts.
The Moscow talks followed two rounds of negotiations since talks with Iran resumed in April after a 15-month hiatus during which the West cranked up sanctions pressure.
Iranian officials have repeatedly insisted on an easing of sanctions and an acknowledgment of the country's right to enrich uranium, conditions that the United States and the European Union have not accepted. Khazayee reiterated those demands on Friday.
Washington and its Western allies accuse Iran of trying to develop nuclear weapons under the cover of a civilian nuclear program, while they have never presented any corroborative evidence to substantiate their allegations. Iran denies the charges and insists that its nuclear program is for peaceful purposes only.
Tehran stresses that the country has always pursued a civilian path to provide power to the growing number of Iranian population, whose fossil fuel would eventually run dry.
Despite the rules enshrined in the Non-Proliferation Treaty (NPT) entitling every member state, including Iran, to the right of uranium enrichment, Tehran is now under four rounds of UN Security Council sanctions for turning down West's calls to give up its right of uranium enrichment.
Tehran has dismissed the West's demand as politically tainted and illogical, stressing that sanctions and pressures merely consolidate Iranians' national resolve to continue the path.
Iran insists that it should continue enriching uranium because it needs to provide fuel to a 300-megawatt light-water reactor it is building in the southwestern town of Darkhoveyn as well as its first nuclear power plant in the southern port city of Bushehr.
Iran plans to construct additional nuclear power plants to provide for the electricity needs of its growing population.
The Islamic Republic says that it considers its nuclear case closed as it has come clean of IAEA's questions and suspicions about its past nuclear activities.
Political observers believe that the United States has remained at loggerheads with Iran mainly over the independent and home-grown nature of Tehran's nuclear technology, which gives the Islamic Republic the potential to turn into a world power and a role model for the other third-world countries.
Edited by: S. Isayev