Taking India by name, US President Barack Obama on Friday said it would be "wrongheaded" to think that global challenges can be met in the absence of "major powers" like this South Asian country.

"One thing I think is absolutely true is that for us to think we can somehow deal with some of the global challenges in the absence of major powers -- like China, India, and Brazil -- seems to me wrongheaded," Obama said in comments that will please India ahead of the planned visit of his Secretary of State Hillary Clinton to New Delhi later this month.

Obama was addressing a news conference at the end of the summit of the Group of Eight Industrialised countries here.

The President also endorsed Prime Minister Manmohan Singh's fresh calls for urgent UN reforms saying the global community will have to "update and refresh and renew" international institutions like the world body that were set up in a different time and place.

Ahead of the summit, Singh made a strong pitch for UN Security Council reforms saying its present structure posed "serious problems of legitimacy."

"The Security Council has not changed at all and its two-tiered membership where five permanent members have veto power was clearly anachronistic," Singh said.

Amidst a growing perception that the importance of the G-8 is diminishing, Obama said, "We have to update and refresh and renew the international institutions that were set up in a different time and place. Some -- the United Nations - date back to post-World War II. Others, like the G8, are 30 years old."

"What's also true is that part of the challenge here is revitalizing the United Nations, because a lot of energy is going into these various summits and these organizations in part because there's a sense that when it comes to big, tough problems the UN General Assembly is not always working as effectively and rapidly as it needs to," Obama said.

The UN has to be reformed and revitalized, he added.

To a question about the adequacy of the G8 as a forum, Obama said there's no sense that such institutions can adequately capture the enormous changes that have taken place during the intervening decades since they were formed.

"What, exactly, is the right format is a question that I think will be debated," he said.

Obama said the G-8 is trying to find the right shape that combines the efficiency and capacity for action with inclusiveness.

"And my expectation is that over the next several years you'll see an evolution and we'll be able to find the right combination," he said, adding, "So I think we're in a transition period."