Mr Ahmadinejad said isolating Iran was "impossible"
Iranian President Mahmoud Ahmadinejad has said international sanctions against his country will not work.
In a TV interview, Mr Ahmadinejad also said that Russia had "made a mistake" in voting last week to condemn Tehran for building a second enrichment plant.
He added that Iran was not obliged to inform UN nuclear watchdog the IAEA of plans to build more nuclear sites.
On Monday Western nations warned Iran against its plans to build 10 more uranium enrichment sites.
Western powers say Tehran is trying to develop nuclear arms, while Iran says its nuclear programme is solely for peaceful civilian purposes.
Mr Ahmadinejad said warnings by Western powers that Iran would be isolated were "ridiculous".
"They need us more than we need them. It is psychological warfare and isolating Iran is impossible," he said.
"Any finger which is about to pull the trigger will be cut off."
He said Iran could produce its own petrol within a week if fuel imports were cut off.
He said that Russia was wrong to join Western countries in voting in the International Atomic Energy Agency (IAEA) on a resolution against Iran over its cover-up of the new uranium enrichment plant near Qom.
"Russia made a mistake. It does not have an accurate analysis of today's world situation," he said.
However, in response to Iran's announcement that it would expand its nuclear programme, a senior Russian diplomatic source said Moscow would join an international consensus on sanctions.
Mr Ahmadinejad's speech came just a day after Iran was warned not to defy international demands by building 10 more uranium enrichment sites.
America's envoy to the UN, Susan Rice, called Iran's announcement "unacceptable", while French Foreign Minister Bernard Kouchner said Iran was playing "an extremely dangerous game".
But the Iranian president said the plan was not a bluff.
"We will follow through on what we say," he said.
The head of Iran's nuclear programme, Ali Akbar Salehi, said on Sunday that Tehran had been provoked into building the new facilities by the vote condemning the Qom site.
Six nations - the US, UK, France, Germany, China and Russia - have been involved in co-ordinating the UN Security Council's position on Iran.
Existing UN sanctions are meant to prevent the flow of any items or technology which might aid Iran in enriching uranium or developing nuclear weapon delivery systems.
The sanctions range from actual sales or supplies to dealings with named individuals.