Ahead of a summit of EU leaders Thursday, Swedish Prime Minister Fredrik Reinfeldt said that concerns about alleged U.S. spying in Europe shouldn't be linked to the efforts to secure a broad European Union-U.S. free-trade agreement, Dow Jones reports.

"I don't think this should be linked together," he said of the trade talks.

The Guardian newspaper reports that White House, Pentagon and State Department officials confirm the United States spied on the phone conversations of 35 world leaders.

The latest report comes as European leaders have united behind a furious Germany to denounce the United States for allegations it spied on its allies, Voice of America said. German Chancellor Angela Merkel said she has made it clear to U.S. President Barack Obama that spying on allies is unacceptable.

Mr. Reinfeldt said some forms of phone tapping and information-gathering activities may be legitimate when used to fight terrorism but not for elected leaders to spy on each other.