The president listed those interests as ranging "from Afghanistan to Iran," including "reducing nuclear stockpiles … reducing the threat of terrorism ... stabilizing the world economy … and finding a sustainable path for energy and dealing with some of the threats of climate change. ... I think there's great potential for concerted action and that's what I think we'll be pursuing."
"A good place to start will be the issue of nuclear proliferation," the president said.
The current nuclear arms START -- or the Strategic Arms Reduction Treaty -- ends Dec. 5, 2009. It was signed in March 1991 and removed more than 75 percent of the strategic nuclear weapons in both countries' arsenals.
More than 3,000 police are battling protesters as numerous groups have planned demonstrations on a wide variety of grievances. Protesters have smashed windows and entered the Bank of Scotland and tried to storm the Bank of England.
Protesters are confronting police over barricades and pelting the cops with eggs and fruit.
Despite the talk of tensions and disagreements among the world leaders at the start of the critical economic summit, Brown praised Obama for his leadership and courage and for providing new hope to the United States and the world.
"Your first 70 days in office have changed America and changed America's relationship with the world," Brown said.
The questions were sharp and focused on the global economic crisis and whether the United States has to shoulder the blame.
"The U.S. certainly has some accounting to do with respect to a regulatory system that was inadequate," Obama said. "I had a law professor who said some are to blame, but all are responsible."
Obama's calls for greater global stimulus have received a chilly reception from European leaders, especially French President Nicolas Sarkozy and German Chancellor Angela Merkel. But as his aides have been doing during the last several days, Obama downplayed those differences.
"I think that the separation between the various parties involved has been vastly overstated," Obama said. "That's just arguing at margins."
Obama kicked off his day at the iconic home of the British prime minister -- 10 Downing St. -- joined by Secretary of State Hillary Clinton and Secretary of the Treasury Timothy Geithner.
Brown is Obama's partner at this summit, working with him to gain consensus on a way to tackle the global economic crisis, but they are facing skepticism that something of real substance can be accomplished.
"I think it is very ill advised to have all the razzmatazz, have all the ballyhoo that they had because there is nothing concrete of any significance that's likely to come out of it," said former British Finance Minister Lord Lawson.
Even though he is thousands of miles away, Obama still has NCAA basketball on the brain. During his news conference this morning with Brown, Obama was asked whether he had a good luck message for the England soccer team that is playing in a World Cup qualifying match.
"I'm in enough trouble back home for picking brackets for the college tournament, stirred up all kinds of controversy. The last thing I'm going to do is wade into European football. … That would be a mistake," Obama said, noting that this is one subject he didn't get a briefing on before his trip.
The first lady and her British counterpart Sarah Brown spent the morning at Maggie's Center, a facility for cancer patients in Central London.
The two women visited with cancer patients, who told them how the center had helped them through the difficulties of the disease.
Maggie's Center is a place for cancer patients and their families to gather for support, comfort and practical advice. Michelle Obama and Sarah Brown also stopped in on the Look Good, Feel Better program, a beauty parlor/makeup session with two female patients.
Michelle Obama talked about her "wonderful" makeup artist and said that the artist volunteers for a similar program in the United States.