BRUSSELS: EU leaders say the distrust of the US over spying could harm the fight against terrorism, after new leaks revealed that Washington has routinely monitored the phone conversations of 35 world leaders.

Allegations of spying overshadowed proceedings at an EU summit in Brussels which was supposed to focus on Europe’s growing refugee crisis.

“(European leaders) stressed that intelligence gathering is a vital element in the fight against terrorism. This applies to relations between European countries as well as to relations with the US,” Herman van Rompuy, the president of the European Council, said in remarks on Friday.

“A lack of trust could prejudice the necessary cooperation in the field of intelligence gathering,” he said.

The Guardian said on Thursday it had obtained a confidential memo suggesting the NSA was able to monitor 35 world leaders’ communications in 2006.

The memo said the NSA encouraged senior officials at the White House, Pentagon and other agencies to share their contacts so the spy agency could add foreign leaders’ phone numbers to its surveillance systems, the report said.

The Guardian did not identify who reportedly was eavesdropped on.

Meanwhile, German officials will travel to the US “shortly” for talks about spying allegations, including whether Chancellor Angela Merkel’s cellphone was monitored by the NSA, the government said Friday.

French President Francois Hollande said “what is at stake is preserving our relations with the United States.” He insisted that “trust has to be restored and reinforced.”