"Even as more nations take on the responsibilities of global leadership," Obama said, "our alliance will remain indispensible to the goal of a century that is more peaceful, more prosperous and more just."
While Tuesday was spent on pageantry, Obama spent much of Wednesday at 10 Downing Street with British Prime Minister David Cameron. While they may share a commitment to get Moammar Gadhafi out of Libya, Obama says that will not require a heavier U.S. military presence.
"I believe that we have built enough momentum that, as long as we sustain the course we're on, he is ultimately going to step down," the president said of Gadhafi.
Obama was granted the honor of being the first U.S. president to speak from the grand setting of Westminster Hall, and he received a deeply friendly welcome. He recounted a history between two countries an ocean apart that was conceived in war but matured into an indispensable global force for economic growth, security, democracy and peace.
"Our action - our leadership - is essential to the cause of human dignity. And so we must act - and lead - with confidence in our ideals, and an abiding faith in the character of our people, who sent us here today," Obama said.
The president received a sustained, standing ovation for his defense of the American-British alliance and how the two "enduring allies" will be a defining force for good in the future, as well.
The Associated Press contributed to this story.