United States President Barack Obama on Wednesday thanked his Afghan counterpart Hamid Karzai on his agreeing to stand for a run-off in elections in Afghanistan, saying it would be a step towards formation of a credible government.

The White House informed media persons that during a telephone conversation with Karzai, Obama underscored that

this decision was in the best interests of the Afghan people.  

'President Obama also called Dr Abdullah Abdullah to express appreciation for his constructive efforts,' the White House said.

Senior US officials said it was not clear whether the run-off would change the timing of Obama's decision on the request for deployment of 40,000 more troops in Afghanistan.