Tehran insists its nuclear programme is aimed at producing electricity so it can preserve its oil and gas for export.
"We are in favour of talks but we will not negotiate with anyone about our right to nuclear technology," Ahmadinejad was quoted as saying by Iranian state television during a trip to Armenia. "Iran will not retreat one iota."
British Prime Minister Gordon Brown said Iran was breaking the nuclear Non-Proliferation Treaty and sanctions could follow.
Israeli premier Ehud Olmert, speaking alongside Brown, said economic measures were "not sufficient".
Ahead of the Rome talks, a U.S. official said Solana would make a "similar offer" to a proposal by Russia's Vladimir Putin: a foreign-built civil nuclear system for electricity without access to "more sensitive" aspects of nuclear technology.
"We've offered diplomacy, they keep rejecting diplomacy, so I really think the ball is in their court," U.S. Undersecretary of State for Political Affairs Nicholas Burns said in New York.
U.S. officials fear Security Council backing for a third sanctions resolution might meet Russian opposition. But British Foreign Secretary David Miliband said in Washington he was confident both Russia and China would support a third round of U.N. sanctions.
U.S. President George W. Bush has said a nuclear-armed Iran could lead to a third world war.
With speculation rife that Jalili's appointment might signal a harder line in Tehran, Larijani said the change should be seen as normal rotation of posts.
"Our country is a democratic country," he said, adding that Jalili was "seven or eight years" his junior and "energetic".
