The new US President met Gordon Brown last July at Downing Street
Gordon Brown has spoken to Barack Obama for the first time since he became US President on Tuesday.
The two leaders spoke by telephone on subjects ranging from the economy to the Middle East.
The prime minister has said the special relationship between the UK and US will be "maintained and strengthened" with Mr Obama in the White House.
The president is due to visit the UK in April for a meeting of G20 leaders focusing on the economic downturn.
President Obama is understood to have initiated the call, which Mr Brown took while on a trip to a Glasgow factory.
Downing Street sources described the conversation as "substantive and friendly".
Afghanistan was discussed but only in general terms and specific matters relating to British troop deployments were not raised.
President Obama has said he wants to send more troops to Afghanistan as part of what analysts believe could be an "Iraqi-style" military surge.
He is keen for other Nato countries to provide more troops.
Senior British army officers have expressed concerns about troops due to leave Iraq within months being transferred directly to Afghanistan.
Other issues that were raised included the situation in the Middle East and the forthcoming meeting of the world's largest economies in London.
On Tuesday Gordon Brown heralded President Obama's inauguration as a "new chapter in both American history and the world's history".
He praised Mr Obama as a "man of great vision and moral purpose" who would tackle the global financial crisis and other problems.