Pope Francis says he has felt "used" by people claiming to be his friend since he became pontiff, in a radio interview touching on the personal side of his papacy.

"I never had so many quote-unquote 'friends' as now. Everyone is the pope's friend," Francis said in a telephone interview with radio station Milenium in his native Argentina.

"I have felt used by people who presented themselves as my friends and whom I hadn't seen more than once or twice in my life. They have used that to their own benefit. But it's an experience we all go through," he told Argentine journalist Marcelo Gallardo, a real-life friend since the days when the pope was bishop Jorge Mario Bergoglio of Buenos Aires.

"Friendship in the utilitarian sense -- let's see what advantage I can gain by getting close to this person and becoming friends -- that pains me," he told Gallardo in the interview, broadcast Sunday.

"Friendship is something sacred. The Bible says to have one or two friends."

Francis, whose papacy began in March 2013, also touched on environmental destruction and religious fundamentalism in the wide-ranging conversation -- a rare interview with a non-religious broadcaster.

Echoing the bold appeal to care for the planet he issued in a sweeping encyclical in June, the pope condemned humankind's "abuse of creation."

"We're not friends of creation. Sometimes we treat it like our worst enemy. Think of deforestation, misuse of water, methods of extracting minerals with elements like arsenic and cyanide that end up making people sick," he said.

Of fundamentalists, he said: "Their mission is to destroy in the name of an idea, not a reality.... They kill, attack, destroy, malign in the name of an ideological god."

The interview came as the pope prepares to visit Cuba and the United States from September 19 to 28.