The FBI and the Justice Department obtained the warrant targeting Carter Page's communications after convincing a Foreign Intelligence Surveillance Court judge that there was probable cause to believe Page was acting as an agent of a foreign power, in this case Russia, according to the officials, WP reports.
Since the 90-day warrant was first issued, it has been renewed more than once by the FISA court, the officials said.
This is the clearest evidence so far that the FBI had reason to believe during the 2016 presidential campaign that a Trump campaign adviser was in touch with Russian agents. Such contacts are now at the center of an investigation into whether the campaign coordinated with the Russian government to swing the election in Trump's favor, WP wrote.
Page has repeatedly denied any wrongdoing in his dealings with the Trump campaign or Russia.
The White House, FBI and Justice Department declined to comment.
Three years before Page became an adviser to the Trump campaign, he came to the attention of FBI counterintelligence agents, who learned that Russian spy suspects had sought to use Page as a source for information.
Read alsoTrump's ex-adviser paid by Russia propagandist RT, Kaspersky Lab – mediaIn that case, one of the Russian suspects, Victor Podobnyy — who was posing as a diplomat and was later charged by federal prosecutors with acting as an unregistered agent of a foreign government — was captured on tape in 2013 discussing an effort to get information and documents from Page. That discussion was detailed in a federal complaint filed against Podobnyy and two others. The court documents in that spy case only identify Page as "Male 1." Officials familiar with the case said that "Male 1" is Page.
In one secretly recorded conversation, detailed in the complaint, Podobnyy said Page "wrote that he is sorry, he went to Moscow and forgot to check his inbox, but he wants to meet when he gets back. I think he is an idiot and forgot who I am. Plus he writes to me in Russian [to] practice the language. He flies to Moscow more often than I do. He got hooked on Gazprom thinking that if they have a project, he could rise up. Maybe he can. I don't know, but it's obvious that he wants to earn lots of money."
The same court document says that in June 2013, Page told FBI agents that he met Podobnyy at an energy symposium in New York, where they exchanged contact information. In subsequent meetings, Page shared with the Russian his outlook on the state of the energy industry, as well as documents about the energy business, according to the court papers.
Read alsoU.S. agents have obtained documents on Paul Manafort in eastern Europe inquiryIn the secret tape, Podobnyy said he liked the man's "enthusiasm" but planned to use him to get information and give him little in return. "You promise a favor for a favor. You get the documents from him and tell him to go f--- himself,"’ Podobnyy said on the tape, according to court papers.
Page has said the information he provided to the Russians in 2013 was innocuous, describing it as "basic immaterial information and publicly available research documents." He said he had assisted the prosecutors in their case against Evgeny Buryakov, who pleaded guilty to conspiring to act in the United States as an unregistered agent of Russian intelligence.
Read alsoSenate intel panel declines Flynn immunity offer in Russiagate "at this time"The FBI routinely obtains FISA warrants to monitor the communications of foreign diplomats in the United States, including the Russian ambassador, Sergey Kislyak. Page is the only American to have had his communications directly targeted with a FISA warrant in 2016 as part of the Russia probe, officials said.