Sen. John McCain. Associated Press/Manuel Balce Ceneta Republican Sen. John McCain of Arizona gave a harsh critique of President Donald Trump's leadership on the global stage in an interview with The Guardian on Sunday.

McCain was asked about Trump's criticism of London Mayor Sadiq Khan in the aftermath of the ISIS-claimed terror attack that rocked the city earlier this month. McCain said that "as far as American leadership is concerned," the US's global standing was better under President Barack Obama than under Trump.

McCain, Obama's 2008 general-election opponent, frequently criticized Obama's foreign policy, while acting as the leading voice on the Senate Armed Services Committee and for the GOP's foreign policy.

"What do you think the message is?" McCain said of Trump's tweet to Khan. "The message is that America doesn't want to lead."

In the rest of the world, McCain added, "they are not sure of American leadership, whether it be in Siberia or whether it be in Antarctica."