He was joined by first lady, Jill Biden.
AP is reporting Biden sat in quiet contemplation by the casket following his peaceful tribute. It was a quiet tribute to the Queen. Bidens was joined on the occasion by U.S. Ambassador Jane Hartley.
Biden is also expected to make a statement of condolence and be at a reception on Sunday evening on the grounds of Buckingham Palace hosted by King Charles III before attending the funeral of the state held at Westminster Abbey on Monday.
The president, who is visiting, is among hundreds of world-class leaders in the capital city to pay their tributes to Queen Elizabeth who passed away on September 8 at the age of 96, after 70 years of reign.
Others who have visited the coffin are New Zealand Prime Minister Jacinda Ardern, Canada Prime Minister Justin Trudeau, Australia Prime Minister Anthony Albanese, and the President of Israel, Isaac Herzog.
The hundreds of thousands of mourners have waited hours to pass by the casket of the Queen.
London's transport authority claims it's preparing for about one million people to travel to central London on Monday to attend the Queen Elizabeth II's funeral.
Transport for London chief Andy Byford confirmed that on Sunday, the capital had witnessed “huge numbers of additional passengers” since the Queen's death on September 8. However, he added that demand could “reach a climax” on Monday, AP reports.
In the UK, around 250 additional train services will be operating, including overnight trains.
Peter Hendy, chairman of Network Rail, said Monday will be the “biggest public transport operation since the London 2012 Olympic and Paralympic Games.”