Hollywood heartthrob George Clooney will host a $6 million fundraising dinner for Barack Obama at his Los Angeles home as the president fills his campaign coffers to battle Mitt Romney.

The event, on May 10, will feature in the "Dinner with Barack" campaign which the president's political braintrust dreamed up to drum up small donations and fire up grassroots supporters.

U.S. leadership has lost some of its luster abroad, suggesting President Barack Obama can't count on as much global euphoria as he gears up for a fierce reelection campaign, a new survey found Thursday.

The report card was particularly dire from Serbia and Iran where approval ratings for the White House were below 10 percent. India, Cyprus, Belarus and Egypt also gave the Obama administration less than stellar marks.

At least 10 American troops could be implicated in a widening sex scandal involving a U.S. Secret Service team preparing for a presidential visit to Colombia, officials said Tuesday.

Government investigators are probing embarrassing allegations that Secret Service agents and U.S. military service members sent to the Caribbean resort of Cartagena ahead of President Barack Obama's weekend visit consorted with prostitutes.

U.S. President Barack Obama said Sunday he expected a "rigorous" probe into a sex scandal involving Secret Service agents, warning he would be "angry" if the claims were proven true.

The incident, which saw 11 Secret Service and five military personnel pulled from their security duties in Colombia at the Summit of the Americas, overshadowed the talks attended by Obama and other regional leaders.

President Barack Obama might be noticing a familiar pattern. Whether it's allegations of Secret Service personnel consorting with prostitutes, candid moments caught live on microphones or launching bombs over Libya, his foreign trips seem to get overshadowed by distractions.

That's been the case on the coast of Colombia, where Obama will wrap up a weekend summit with a news conference that may well force him to confront the latest troubles — misconduct claims against Secret Service and military personnel assigned to make Cartagena secure for his visit.

Talks between Iran and six world powers in Istanbul on Tehran's nuclear program, the first in 15 months, began Saturday in a "positive atmosphere," a European Union spokesman said.

"There is a positive atmosphere. ... There is a desire for substantive progress," Michael Mann, spokesman for EU foreign policy chief Catherine Ashton, told reporters.

U.S. Secretary of State Hillary Clinton on Friday asked her Chinese counterpart to convey U.S. concern to Beijing's ally North Korea after its defiant but unsuccessful rocket launch.

Clinton, who was heading Friday to a summit in Colombia, spoke by telephone with Chinese Foreign Minister Yang Jiechi as she sought a "unified way to speak out and condemn this action," State Department spokesman Mark Toner said.

Four explosive devices went off in Colombia late Friday ahead of an Americas summit, without causing any casualties or damage to buildings, police said.

The first two crude low-power bombs exploded near the U.S. Embassy in Bogota shortly after the arrival in Colombia of U.S. President Barack Obama, who is due to take part in the summit in the resort city of Cartagena.

French President Nicolas Sarkozy and U.S. President Barack Obama urged Iran on Thursday to take upcoming nuclear talks seriously and suspend sensitive atomic activities.

"They called on Iran to seize the opportunity of the resumption of talks with the Six (world powers) to engage in serious negotiations and suspend all sensitive nuclear activities," Sarkozy's office said in a statement after the two leaders held video-conference talks.

Presidents Nicolas Sarkozy of France and Barack Obama of the United States demanded Thursday that Syria respect the terms of a peace plan drawn up by a U.N. envoy and the Arab League.

The French presidency announced the joint call in a statement after the leaders held videophone talks on a series of world crises, and warned that Bashar al-Assad's regime would be "judged on its actions".