He said: "The Royal Liverpool Philharmonic has strong musical and personnel ties with the United States.
"We very much regret Roger has been placed under such pressure that he has decided he has no choice but to withdraw.
"The people and institutions of this great city should have the confidence as we prepare for 2008 to both host visits from the leaders of democratic states, and to express through its many voices and artists its commitment to building international peace and understanding."
A Foreign Office spokesman said: "The foreign secretary is delighted that he will be bringing US secretary of state Condoleezza Rice to Liverpool.
"He is looking forward to showing her, and through the visit the world, what a tremendous, thriving city Liverpool is, as it prepares to become European Capital of Culture 2008.
"We are grateful to all those who are hosting events for us."