U.S. President Barack Obama has rolled back George W. Bush's policy of isolating Iran, and U.S. officials have sought out Iranian representatives at recent international meetings.
Asked if he had had dialogue with Iranian Foreign Minister Manouchehr Mottaki at Friday's gathering, Holbrooke replied: "No dialogue. I ran into the foreign minister as we were milling around and we said 'hello' and chatted for about a minute or two."
The United States has joined Russia, China, France, Germany and Britain in asking the European Union's foreign policy chief to find a diplomatic solution to Iran's disputed nuclear programmes.
Iranian President Mahmoud Ahmadinejad said in remarks published on Friday that Tehran favoured dialogue with world powers over its nuclear programme and would soon give its official response to the invitation to hold talks.
The Obama administration has said it is prepared to meet Iran without preconditions, but it has also made clear that suspension of enrichment remains the goal.
Iran, which says its nuclear programme is to generate electricity, has boasted of now running 7,000 uranium centrifuges, which can have civilian and military uses, and has vowed not to stop uranium enrichment.
Holbrooke also told a news conference that Iran had pledged over $300 million (203 million pounds) of the more than $5 billion in aid promised for Pakistan on Friday by international donors worried that an economic meltdown in the South Asian nuclear-armed country could fan popular support for al Qaeda and other militant groups.
"We were impressed and pleased at the fact that the speech by Foreign Minister Mottaki yesterday was so positive in tone towards the issues in Pakistan," Holbrooke said.
(Reporting by Linda Sieg)
