George W Bush arrived at Downing Street early on Monday, the second day of his UK visit, for talks with Prime Minister Gordon Brown.
The two men were expected to focus on the Middle East and Iraq as well as high oil and fuel prices.
Mr Bush's discussions with the prime minister followed an earlier meeting with ex-PM and now Middle East envoy Tony Blair.
At a joint news conference, Gordon Brown said UK troops for Afghanistan would be increased to their highest level yet.
First Lady Laura Bush visited the Charles Dickens museum in London and was shown the novelist's original manuscripts.
From Downing Street, George Bush is travelling to Northern Ireland for talks with assembly leaders.