A book published in France says the US regularly monitored French President Jacques Chirac's phone calls.
The Bush-Chirac relationship is said to be "irreparable"
The book, which charts the breakdown of the leaders' relationship in the run-up to the Iraq war, says several sources reported the surveillance.
The US told a senior French military official the French-US relationship at a personal level was "irreparable".
The book, Chirac contre Bush - l'autre guerre (Chirac versus Bush - the other war), comes out on Wednesday.
The two leaders were at loggerheads over the war in Iraq, which culminated with Mr Chirac pledging to use his UN veto against the war.
"The relationship between your president and ours is irreparable on the personal level. You have to understand that President Bush knows exactly what President Chirac thinks of him," a US official is reported as telling a senior French military official in the book by journalists Henri Vernet and Thomas Cantaloube.
Surveillance was possible because Mr Chirac rarely uses secure phone lines, except in scheduled calls to world leaders, Mr Vernet told BBC News Online.
Mr Chirac and the then French Foreign Minister Dominique de Villepin led a very small team inside the Elysee palace which made decisions on France's strategy on Iraq, Mr Vernet says.
They were aware their policy was popular with French public opinion and that as such there were "no moderating elements" inside the team, according to an Elysee source close to the team, Mr Vernet says.
The book's two authors, who are journalists based in Paris and Washington for Le Parisien newspaper, investigated the US-France relationship for a year as the Iraq crisis unravelled, speaking to various military and security sources.
UN bug claims
The book lends further credence to reports that the UN is routinely bugged by larger powers to monitor diplomatic conversations.
In the run-up to the Security Council sessions on Iraq in early 2003, the French and members of other European delegations had to meet in the German mission's anti-bugging glass cage to avoid their conversations being monitored, Mr Vernet says.
In the early 1980s, Jeane Kirkpatrick, the then US Ambassador to the UN, warned her French counterpart through sign language that Washington was listening in, Mr Vernet says.
Earlier this year, a former UK government minister, Clare Short, said the British had spied on UN Secretary General Kofi Annan at the UN's headquarters in New York in the run-up to the Iraq war.