TEHRAN (Tasnim) A senior adviser to Leader of the Islamic Revolution Ayatollah Seyed Ali Khamenei reaffirmed the country's commitment to uranium enrichment, saying Tehran is drafting a counter-proposal in response to a recent US offer on its nuclear program.

Ali Shamkhani, a political adviser to Ayatollah Khamenei, told Lebanon's al-Mayadeen television on Wednesday that Iran is preparing a new response following receipt of the latest American proposal.

After receiving the American proposal regarding the Iranian nuclear program, we are now preparing our new counter-proposal, Shamkhani said.

He criticized the US proposal as lacking in substance and failing to address a key demand from Tehran.

There is no mention whatsoever of lifting sanctions in the latest American proposal, even though the issue of sanctions is a fundamental matter for Iran, he stated.

Shamkhani stressed that Iran will never relinquish its natural rights.

He said Iran will not allow the US to succeed in its efforts to dismantle Tehrans peaceful nuclear program or reduce uranium enrichment to zero.

Addressing a ceremony marking the 36th anniversary of the death of Ayatollah Ruhollah Khomeini, the founder of the Islamic Republic, Ayatollah Khamenei reiterated that uranium enrichment is the key to Irans nuclear issue.

He dismissed Washingtons demand that Iran halt all uranium enrichment.

His comments followed recent statements by US President Donald Trump, who said Iran would not be allowed any enrichment of uranium.

US media reports on Tuesday indicated that the Trump administration is considering a proposal allowing limited low-level enrichment on Iranian soil for an unspecified period.

Iran and the United States have so far held five rounds of indirect negotiations aimed at reviving or replacing the 2015 nuclear agreement, formally known as the Joint Comprehensive Plan of Action (JCPOA).

However, progress has stalled over the US insistence that Iran end all uranium enrichment under any new deal.

Iranian officials have consistently rejected the demand.