Obama, a Democrat, has been highly critical in the past of Bush's policies toward Iran and has promised that if elected he would pursue a policy of greater engagement aimed at persuading Tehran to abandon its nuclear enrichment program.

But in a rare signal of solidarity with the current Republican administration, Obama told a news conference in Paris on Friday that Iran should not wait for the next U.S. president to try to reach a deal over its nuclear program.

He also praised Bush's decision to send senior U.S. diplomat William Burns to talks in Geneva with Iranian officials.

"Bill Burns is a very serious guy. And the Iranians should take that gesture seriously," Obama told Reuters in an interview on Saturday as he flew back from a weeklong tour abroad.

Obama, who is running against Republican John McCain in the November election, is seeking to burnish his foreign policy credentials. He travelled to Afghanistan, Iraq, Kuwait, Jordan, Israel, Germany, France and Britain.

Iran was a key topic in many of the meetings he had with leaders of those countries.

Iran has refused demands to freeze sensitive atomic work the West fears is aimed at making bombs. Tehran says the nuclear program is aimed at the peaceful purposes of generating electricity.

Envoys from the United States, Russia, China, France, Germany and Britain -- the so-called sextet of world powers -- attended the Geneva meeting.

"I want the Bush administration to be successful in working with the Europeans to get Iran to stand down on its nuclear weapons program," Obama said.

Iranian President Mahmoud Ahmadinejad was quoted on Iranian state television saying his country has more than 5,000 active centrifuges for enriching uranium, suggesting a rapid expansion of nuclear work.

IMPRESSIONS OF MALIKI, KARZAI

Also in the Reuters interview, Obama talked of his impressions of Iraqi Prime Minister Nuri al-Maliki and Afghan President Hamid Karzai, both of whom he met during the trip.

"I think Maliki has made some tough choices, particularly going into Basra and Sadr City to disperse the Shia militias. I'm glad to see that he is eager to take more responsibility for his country's own security," Obama said.

"I think he recognizes that the Iraqi government both has to become more efficient and more inclusive. Whether he understands the degree to which that has to happen ... I can't tell," he added.

The Democratic candidate said Karzai is "very smart and charming" and has a vision for Afghanistan's future. But he said he needed to move to rid his government of corruption and combat the narcotics trade.

"I told President Karzai that I thought that he needs to really focus on issues of corruption and counternarcotics and to counter the narcotics trade much more aggressively than has been done so far," he said.

Obama has called for a renewed focus on Afghanistan, including the addition of two U.S. brigades and has called on European countries to do more to help stabilize the increasingly violent country.