"We face a consequential choice -- and make no mistake, it is a choice" McCain, the 2008 Republican presidential nominee, told the Republican National Convention. "We can choose to follow a declining path, toward a future that is dimmer and more dangerous than our past. Or we can choose to reform our failing government, revitalize our ailing economy and renew the foundations of our power and leadership in the world."
McCain called on America to embrace presidential nominee Mitt Romney, who McCain defeated in the 2008 primary.
McCain said the nation has drifted from its traditions of global leadership, making the challenges the country faces at home and abroad harder to solve.
"We can't afford to cause our friends and allies -- from Latin America to Asia, Europe to the Middle East, and especially in Israel -- to doubt America's leadership," McCain said. "We can't afford to give governments in Russia and China a veto over how we defend our interests and the progress of our values in the world."
The country also can't afford to jeopardize its security and the safety of the men and women who defend it "because their government leaks the secrets of their heroic operations to the media," McCain said to applause and cheers.
He also criticized President Obama for withdrawing U.S. combat troops from Afghanistan in 2014, saying such a plan before peace is achieved and sustained "discouraged our friends and emboldened our enemies."
The looming reduction of the defense budget by $500 billion through sequestration, in addition to the nearly $500 billion in cuts already being made, is something the country can't afford, McCain said.
"His own secretary of defense [Leon Panetta] has said that cutting our military by nearly $1 trillion would be 'devastating,'" McCain said.
And yet, Obama hasn't taken a leadership role in "in preventing this crippling blow to our military."
"But most of all, we can't afford to abandon the cause of human freedom," McCain said. "When long-suffering peoples demand liberation from their jailers and torturers and tyrants, the leader of the free world must stand with them. Unfortunately, this is not happening."
He charged Obama is standing by as Iranians and Syrians fight against oppressive governments.
"In other times, when other courageous people fought for their freedom against sworn enemies of the United States, American presidents -- both Republicans and Democrats -- have acted to help them prevail," McCain said. "Sadly, for the lonely voices of dissent in Syria and Iran and elsewhere ... our president is not being true to our values."
He said people around the world have told him they still have faith in America but wonder whether Americans still have faith in themselves.
"I trust that Mitt Romney has that faith, and I trust him to lead us," McCain said. "I trust him to know that if America doesn't lead, our adversaries will, and the world will grow darker, poorer and much more dangerous."