Prime Minister Gordon Brown said he was looking forward to working with new US President Barack Obama. Mr Brown said: "I would like to offer my sincere congratulations to Barack Obama on winning the Presidency of the United States. "I would also like to pay tribute to Senator McCain who fought a good campaign and has shown the characteristic dignity that has marked a lifetime of service to his country. "The relationship between the United States and the United Kingdom is vital to our prosperity and security. "Barack Obama ran an inspirational campaign, energising politics with his progressive values and his vision for the future. "I know Barack Obama and we share many values. "We both have determination to show that government can act to help people fairly through these difficult times facing the global economy. "And I look forward to working extremely closely with him in the coming months and years." Conservative leader David Cameron said: "In electing Barack Obama, America has made history and proved to the world that it is a nation eager for change. This has been an exciting and inspirational contest with two great candidates. "In these difficult times, people everywhere are crying out for change. Barack Obama is the first of a new generation of leaders who will deliver it - he has my wholehearted congratulations. "This is an important moment not just for America but for the world. Barack Obama's victory will give people a new opportunity to look at the United States and see her for what I believe she is - a beacon of opportunity, freedom and democracy."