Afghan President Hamid Karzai is due to begin a four-day U.S. trip Tuesday in which he will meet U.S. President Barack Obama for crucial talks on the future of the American presence in Afghanistan.

Friday's meeting at the White House will come just days after Obama put the finishing touches to his security team, having named his picks to head up the State Department, Pentagon and CIA.

A soldier serving with the NATO force in Afghanistan was shot dead by a man in Afghan army uniform, the latest in a series of "insider" attacks, the alliance said Tuesday.

More than 60 troops from the force were killed in 2012 in a surge of insider attacks that have shaken relations between the alliance and Afghanistan as the U.S.-led soldiers try to train up the local army and police to battle Taliban militants.

President Hamid Karzai on Monday left Afghanistan for talks with Barack Obama in Washington to focus on security in his war-torn country after NATO combat troops withdraw in 2014, his office said.

During his three-day official visit, a decision could be made on how many US troops will stay in Afghanistan after 2014, officials have said.

The Taliban on Saturday warned of a prolonged war in Afghanistan if any foreign troops stay after the end of 2014, as Kabul and Washington prepare to discuss the "residual" U.S. security presence.

President Barack Obama and President Hamid Karzai will hold talks in the U.S. next week on a long-term security pact between the two countries, with U.S. troops remaining in Afghanistan at the top of the agenda.

The female Afghan police officer who shot dead a NATO adviser in Kabul is an Iranian national who wanted to kill senior security members, officials said Tuesday.

On Monday an Afghan police officer opened fire on a NATO civilian adviser inside police headquarters, killing the adviser who sources said was American.

President Hamid Karzai on Saturday blamed foreigners for most of the corruption in Afghanistan and said the withdrawal of NATO troops in 2014 would help rid the country of graft.

More than 11 years after a U.S.-led invasion led to billions of dollars in aid flowing into one of the world's poorest countries, Afghanistan ranks among the most corrupt nations in the world.

President Hamid Karzai on Thursday welcomed the announcement that Britain will pull thousands of troops out of Afghanistan next year, saying his country was ready to take over security responsibilities.

British Prime Minister David Cameron on Wednesday said that he will withdraw almost half of the country's 9,000 troops from Afghanistan next year as NATO hands over to Afghan forces.

Afghan President Hamid Karzai said Saturday a suicide attack that wounded the country's spy chief was planned in neighboring Pakistan.

Asadullah Khalid, who heads the National Directorate of Security (NDS), was targeted by an attacker with a bomb hidden in his underwear posing as a Taliban peace envoy in Kabul on Thursday.

Afghanistan's intelligence chief was wounded in an assassination attempt in Kabul on Thursday, officials said.

Asadullah Khalid, head of the National Directorate of Security (NDS), was injured in a grenade attack in a guesthouse, police and a senior government official told Agence France Presse.

A roadside bomb killed 10 civilians, including a woman and five children, and wounded eight when it ripped through a van in southern Afghanistan on Thursday, officials said.

The families were on their way to visit a relative who had recently returned from Mecca when their vehicle was hit in Dih Rawud district in rural Uruzgan province, district governor Nematullah Khaliqi told Agence France Presse.