"Even the proposal to suspend enrichment, which we regard as illogical, can be discussed in negotiations," Foreign Minister Manouchehr Mottaki told a press conference.
"We do not see any logic in suspension so we are ready to explain and express that to the other side.
"The resolution is illegal and politically motivated and has no value for us," he added.
The US, which is leading the campaign against Iran's nuclear program, dismissed Mr Mottaki's comments.
A package of economic and other incentives was offered to Iran in June, but Tehran's self-imposed deadline of August 22 to respond was deemed too long.
Iran's case was then sent back to the UN Security Council, which passed a resolution demanding Tehran halt the sensitive atomic work by August 31 or face possible sanctions.
The country has repeatedly rejected suspension as a pre-condition to negotiations aimed at ending the long-running standoff with the West over its nuclear program.
Iran says it wants to enrich uranium to make fuel for nuclear power plants. The West accuses Iran of using its civilian nuclear program as a smokescreen to build atomic bombs.
Negotiations 'should guarantee rights'
Mr Mottaki said any negotiations should "guarantee obtaining the Iranian people's rights as well as clearing up any questions, ambiguities and concerns regarding the Islamic republic's peaceful nuclear activities."
"We will not back down on our legitimate rights under any conditions."
President Mahmoud Ahmadinejad rejected the resolution on Tuesday, saying: "If they think they can use a resolution as a stick against us, they should know that Iranian people do not bend to language of force."
Deputy Foreign Minister Alireza Sheikh-Attar has said that Iran could cope with sanctions.
"The government has considered necessary measures to confront any sanction. Under the worst conditions, we have the capability to face threats and find foreign and domestic alternatives," the official news agency IRNA quoted him as saying.
A US State Department spokesman noted the range of "different messages" that have been coming out of Iran over the past month.
"We're not looking for comments on the periphery, we're looking for an official response from the Iranians to the UNSC resolution," said Gonzalo Gallegos.