Queen Elizabeth II dies — follow the latest news as the world mourns
Leaked documents show dignitaries will travel to Westminster Abbey in escorted coaches and “because of tight security and road restrictions” they will be required to leave their private state vehicles behind.
Only heads of state and their spouses or partners will be invited to the event on September 19, because of limited space in the historic building, it has been reported.
The White House confirmed that Mr Biden will attend the funeral with his wife Jill.
Politico reported that a communication from the Foreign, Commonwealth and Development Office was sent to embassies late on Saturday.
The department said it “regrets that, because of limited space at the state funeral service and associated events, no other members of the principal guest’s family, staff or entourage may be admitted", it was reported.
Heads of state unable to attend may choose someone else as their official representative.
Queen Elizabeth with 11 US presidents — in pictures
The document said world leaders were urged to travel on commercial flights and told they could not use helicopters to travel around the UK.
The office urged commercial travel “where possible”, Politico said.
“Multiple and comprehensive layers of security will be in place across London and at all the official venues used for the state funeral and associated events,” the document seen by Politico said.
The document also set out some of the engagements for heads of state surrounding the funeral.
Queen Elizabeth's visits to the Mena region - in pictures
This includes receptions hosted by the king and the new Foreign Secretary James Cleverly, an offer to visit the queen's body when it is lying in state, and a chance to sign a book of condolence at Lancaster House.
It reported that foreign leaders will be invited to deliver a tribute to the queen while at Lancaster House, but it can only last up to three minutes.
And “because of the extensive ceremonial programme related to the state funeral and the logistical challenges, requests for bilaterals will not be considered on this occasion", the leaked document said.
The office has been approached for comment.