British and other European intelligence agencies intercepted communication between members of Donald Trump's campaign team and Russian officials and passed that information on to the United States, intelligence sources said.
Anonymous U.S. and British intelligence sources told The Guardian that the Government Communications Headquarters intelligence agency played a crucial role in telling U.S. intelligence agencies about the alleged communication between Trump's associates and Russian intelligence operatives.
A source said GCHQ first became aware of suspicious "interactions" between Trump and suspected agents of Russia in late 2015 after picking up the contact during routine surveillance of Russians. The agency then passed that information to U.S. officials as a routine exchange of information.
In the following months, different European agencies targeting the same Russians began to see a pattern of connections, sources said. Until summer 2016, other countries including Germany, Estonia, Poland, Australia, and possibly France and the Netherlands, passed on intelligence related to Trump associates and Russians.
U.S. and British sources acknowledged that GCHQ played an early, prominent role in initiating the FBI's investigation on the link between Russia and Trump, which began in late July 2016.
The sources also said the FBI and CIA were slow to appreciate the extensive nature of the contacts, in part due to a U.S. law prohibiting intelligence agencies from examining the communication of U.S. citizens without a warrant.
"It looks like the [U.S.] agencies were asleep," one source told The Guardian. "[European agencies] were saying: 'There are contacts going on between people close to Mr. Trump and people we believe are Russian intelligence agents. You should be wary of this. ... The message was: 'Watch out. There's something not right here.'"
Anonymous sources told CNN that British and European intelligence agencies captured communications during routine surveillance of Russian officials and other Russians known to western intelligence. The intelligence agencies were not proactively targeting Trump associates but rather picked up communications during "incidental collection."
The sharing of intelligence will likely be part of the Senate Intelligence Committee's investigation into Russia's efforts to meddle with the 2016 U.S. presidential election.
"If foreign intelligence agencies share information with U.S. intelligence, and it's relevant to the investigation, then of course the intelligence committee will look at it," a source close to the Senate investigation told CNN.
The House and Senate intelligence committees, and the FBI are all investigating Russia's alleged meddling in the 2016 U.S. presidential election.
In March, an official said the White House apologized to Britain after press secretary Sean Spicer suggested GCHQ wiretapped Trump Tower during his presidential campaign at the request of former President Barack Obama.