KABUL - US President Barack Obama, keen to reset relations with Afghanistan that soured under longtime president Hamid Karzai, has invited the leaders of Afghanistan's new unity government to visit the White House early next year.

The new Afghan leadership comes at a crucial time as American combat troops draw down after 13 years and a remaining US force of about 10,000 shifts to a support role for Afghan security forces taking over the fight against Taliban insurgents.

Afghan President Ashraf Ghani and the country's new chief executive, Abdullah Abdullah, spoke with Obama via video conference on Wednesday night, a White House statement said.

Obama congratulated the two former rivals on forming their unity government, which was sworn in last month after a prolonged election dispute in which both candidates claimed victory.

He reiterated an invitation to the US for both leaders that was made in a letter soon after the government was formed.

Obama discussed ways to strengthen the Afghan police and army as well as budget reforms to shore up the cash-strapped Kabul government's finances.