The White House added Instagram to its social media portfolio on Wednesday, as it posted a picture of a helicopter with President Barack Obama and his family taking off on a trip to Africa.

"The First Family takes off for a three-country trip across Africa #MarineOne #ObamaInAfrica Follow @WhiteHouse for more!," said the caption for the picture of the presidential helicopter leaving the White House.

U.S. President Barack Obama and Afghan leader Hamid Karzai support the idea of holding talks with the Taliban in its Qatar office, the White House said Tuesday, reviving hopes for a peace process.

The announcement came despite a brazen Taliban assault on the Afghan presidential palace in the heart of Kabul Tuesday, in which three security guards and all five assailants were killed in an hour-long gunbattle.

U.S. Secretary of State John Kerry has vowed new support for Syria's rebels but beyond tougher talk, it remains unclear how much has changed.

Kerry met with fellow opponents of Syrian President Bashar Assad's regime during talks Saturday in the Gulf Arab monarchy of Qatar, a stalwart supporter of the Sunni Muslim rebels.

U.S. President Barack Obama understands Moscow's concerns over his call for both countries to reduce their nuclear weapon stockpiles, Russia's foreign minister was reported as saying on Saturday.

Obama had told his Russian counterpart Vladimir Putin during their meeting at the G8 summit that he would call for the two countries to cut the number of their atomic weapons, Foreign Minister Sergei Lavrov said in a television interview published on Saturday.

President Barack Obama Friday nominated his special envoy for Middle East peace, David Hale, as the next U.S. ambassador to Lebanon, as part of a shake-up of the administration's regional team.

Hale took over the Middle East post after veteran peacemaker George Mitchell left in May 2011, disheartened by a lack of progress in the peace talks.

U.S. President Barack Obama repeatedly called British Finance Minister George Osborne "Jeffrey" at the G8 summit, media reported on Thursday.

The U.S. president said three times that he agreed fully with "Jeffrey" during his presentation on G8 host Britain's plans to crack down on tax evasion, leaving Osborne red-faced.

President Barack Obama on Wednesday defended U.S. Internet and phone surveillance programs which sparked alarm in Europe, saying American spies were not "rifling" through the emails of German and French citizens.

Obama insisted that the programs run by the super secret U.S. eavesdropping service the National Security Agency (NSA) were legal and limited and were a vital tool in the fight against global terrorism.

The Afghan government on Wednesday lashed out at U.S. efforts to broker peace with the Taliban, suspending crucial security talks with Washington and threatening to boycott prospective contacts with the insurgents in Qatar.

Kabul issued two strongly worded statements threatening to sabotage U.S. efforts to start talks with the Taliban, just one day after its foes opened an office for dialogue in the tiny Gulf emirate.

U.S. President Barack Obama will on Wednesday propose the United States and Russia cut strategic nuclear warheads by a third and reduce tactical nuclear arsenals in Europe, a U.S. official said.

Obama, who will make the proposals in a major speech in Berlin, will also commit to attending a nuclear security summit in The Hague next year, and to holding a similar meeting in the final year of his presidency in 2016.

Barack Obama arrived for his first visit as U.S. president to Berlin on Tuesday for talks with German Chancellor Angela Merkel and a major open-air speech at the city's Brandenburg Gate.

Obama arrived at Berlin's Tegel Airport from Northern Ireland where he and Merkel took part in a G8 summit dominated by the bloodshed in Syria and a bid by the European Union and the United States to create the world's biggest free trade area.