KABUL -- President Barack Obama welcomed Afghan President Hamid Karzai's election with as much admonishment as praise, telling America's partner in war that he expects a more serious effort to end corruption in his government and ready his nation to ultimately defend itself.

"I emphasized that this has to be a point in time in which we begin to write a new chapter," Obama said in describing his congratulatory phone call to Karzai. The U.S. president said that when Karzai offered back assurances, Obama told him that "the proof is not going to be in words. It's going to be in deeds."

Obama's message of stern solidarity came as he considers sending tens of thousands more U.S. troops into the war zone in Karzai's country.

Karzai won a second term Monday when competitor Abdullah Abdullah pulled out of the Nov. 7 runoff for fear it would be doomed by fraud just as the first voting in August was. The fraud-marred election cost Karzai international credibility.

The White House put its weight behind the legitimacy of the outcome after helping to broker a runoff that never happened. Obama called the process "messy" but said Karzai won in accordance with Afghan law. The White House repeatedly said Abdullah had pulled out purely for his own political and personal reasons.