US President Barack Obama visited Afghanistan on an unannounced trip on Friday during which he addressed US soldiers at Bagram airfield and praised them for their sacrifices. Obama could not fly to capital Kabul due to bad weather and had a phone conversation with Afghan President Hamid Karzai. Addressing the troops, he said important progress had been made in the war and that they could be proud that there are fewer areas under Taliban control now. His visit lasting few hours was the second during his Presidency and came amidst Wikileaks disclosures, which quoted US diplomats terming Karzai as weak and his Government as corrupt. Both leaders had met at the NATO summit last month where it was decided to hand over security responsibility to Afghan security forces by 2014. US administration is in the middle of conducting a review over Afghan war, one year after President Obama announced to send additional 30 thousand troops. Obama's Afghan war adviser Douglas Lute told reporters aboard Air Force One that neither topic came up during their 15-minute phone conversation with Afghan President.