The US ambassador in Kabul has written to the White House to oppose sending thousands more troops to Afghanistan.

BBC: US opinion on Afghan strategy

After Wednesday's ceremony at the US state department, Croatia's ambassador said his country intended to assume its share of the security burden in Afghanistan, where Nato leads the 55, 000-strong International Security Assistance Force (Isaf).

BBC: Nato welcomes Albania and Croatia

The new US Secretary of State John Kerry has still not appointed a successor to Ambassador Marc Grossman who stepped down as Special Representative to Afghanistan and Pakistan at the end of last year.

BBC: Barack Obama delivering his State of the Union address