Amid unprecedented policy shifts and loose rhetoric on foreign policy from the Trump administration, Arizona Sen. John McCain said that American leadership was better under former President Barack Obama.

McCain, a frequent Republican critic of President Donald Trump, slammed the former real estate mogul in an interview with The Guardian, saying the world is "not sure of American leadership, whether it be in Siberia or whether it be in Antarctica."

McCain’s comments in a story published Sunday were a direct response to the president’s Twitter habits. After the recent terrorist attacks on the London Bridge, Trump used 140 characters to blast London Mayor Sadiq Khan, the first Muslim mayor of a major western European city.

“Pathetic excuse by London Mayor Sadiq Khan who had to think fast on his ‘no reason to be alarmed’ statement,” Trump wrote on June 5, in an attempt to use the attacks, which left eight people dead, to defend his controversial travel ban on refugees and immigrants from certain Muslim-majority nations.

The legality of the travel ban is still being dueled out in the courts, but criticism from the entire political spectrum ensued, as the president’s statement mischaracterized what the mayor said and also the message it sent to one of the United States’ most crucial allies.

“What do you think the message is? The message is that America doesn’t want to lead,” McCain said.

Trump’s loose, freewheeling approach to foreign policy could continue to have larger ramifications for the country’s diplomatic relations. The president reportedly won’t visit the United Kingdom until he feels the British public would welcome him, he told U.K. Prime Minister Theresa May in a phone conversation in recent weeks.