Cameron, 43, became prime minister when Labor's Gordon Brown stepped down Tuesday. That ended the political deadlock after last Thursday's elections gave Cameron's Conservative Party a plurality, but not majority, of seats in Parliament's House of Commons.
The Conservatives won 306 seats in the 650-seat House of Commons. Brown's Labor Party was next at 258 and the Liberal Democrats third with 57, creating a hung Parliament.
Brown, as sitting prime minister, could have tried to form a government but stepped aside leaving Cameron to turn to the Nick Clegg and the Liberal Democrats to put together a working majority.
The economy will be first order of business for Cameron, who was greeted on his first full day in office with word unemployment in the United Kingdom is at its highest since 1994.
The coalition, the first such ruling agreement in Britain since World War II, is an unexpected mix and as a commentator for American Public Media's Marketplace Morning Report related, "the cynics are saying it may not be too long before the two governing parties are fighting like ferrets in a sack."
Clegg, however, said he doesn't see such conflicts as inevitable.
"I hope this is the start of the new politics I have always believed in -- diverse, plural, where politicians of different persuasions come together, overcome their differences in order to deliver good government for the sake of the whole country," he said, even while admitting his party members have "many questions, maybe many doubts."
Collected below are 11 images from the most devastating car bomb attacks on Iraq since 2004.
Kagan, if confirmed, would be the fourth woman on the country's highest court and, at 50, the youngest member who could have a voice on U.S. jurisprudence for decades.
U.S. President Barack Obama was to announce the nomination Monday, several media outlets reported, all citing unnamed sources.
Obama has been seeking a replacement for Justice John Paul Stevens since Stevens, 90, announced in April his intention to resign at the end of the current Supreme Court term. Stevens has been on the court since December 1975.
Kagan's selection isn't expected to alter the philosophical balance of the court if she replaces Stevens, who has led the more liberal side of the court. But she will be the first person in decades nominated to the court who isn't coming from a judgeship, and a lack of published judicial opinions and legal writings leave most of her stances unknown.
She missed out on a chance to join the federal appeals court when the U.S. Senate in 1999 never voted on her nomination by U.S. President Bill Clinton. She served as a clerk for Justice Thurgood Marshall. She graduated from Harvard Law School, where she later served as dean from 2003 until joining the Obama administration as solicitor general.
Troops from Britain, France, Poland and the United States marched alongside 10,000 Russian forces while about two dozen world leaders attended the 65th anniversary, the BBC reported Sunday. The parade also featured tanks, ballistic missiles and a fly-over of 127 aircraft.
Russian President Dmitry Medvedev told spectators lessons from World War II "urge us to show solidarity."
"Peace is still fragile and it is our duty to remember that wars do not start in an instant," Medvedev said. "It is only together that we shall be able to counter modern threats."
Victory Day parades involving more than 102,000 service personnel and more than 200,000 veterans were conducted in 36 Russian cities, Russian news agency RIA Novosti reported.
Medvedev said the march on the Red Square "symbolizes our readiness to defend peace, to prevent the revision of the results of the war, to prevent new tragedies."