The CIA took an interest in Jeremy Corbyn's visits to countries with Marxist regimes in the same period that he was being courted by a Communist spy in London, declassified files show.
The US spy agency made references to Mr Corbyn visiting El Salvador and Grenada in his days as a backbench MP, including a trip to a conference organised by a trade union with links to the Soviet Union and guerilla fighters.
The files form part of a cache of documents that show deep concern within the CIA about the Labour Party in general during Margaret Thatcher’s premiership, when the agency regarded Labour as “a threat to US interests”.
Mr Corbyn was not the only Labour MP the CIA was keeping tabs on; the then Labour leader Neil Kinnock crops up almost 40 times in the files.
In 1986, when Ronald Reagan was president, the US Embassy in San Salvador cabled Washington with details of Mr Corbyn’s attendance at a conference of the El Salvador trade union Fenastras.
The union was described as being connected to Marxist guerillas fighting the US-backed military government in the country’s civil war, as well as being connected to the World Federation of Trade Unions, considered a Soviet front.
The cable said "British Labor MP Jeremy Corbyn" had allowed his name to be used on a Fenastras newspaper advert.
The US Government regarded Fenastras to be a front for the Farabundo Marti National Liberation Front (FMLN) which fought the right-wing government using arms supplied by Cuba and the Soviet Union.
Mr Corbyn's trip to El Salvador from November 8-17 that year, according to his entry in the parliamentary register of members' interests, was "part funded by the El Salvador Solidarity Committee".
In the same year he visited Cuba and Nicaragua "with some internal travel assistance from the Cuban Government", as well as making a second trip to El Salvador.
Mr Corbyn's name also appears on a CIA global media monitoring list from 1984, referring to a visit he made in 1979 to Grenada. The Caribbean island was governed by a Marxist-Leninist leader at the time of Mr Corbyn's visit and had close links to Cuba.
The document states: "British Labor MP Jeremy Corbyn quoted on his visit to island."
The CIA was not alone in keeping tabs on Mr Corbyn, then a backbench Labour MP on the opposition benches.
The Czechoslovakian secret service, the StB, had a file on Mr Corbyn in the 1980s, when one of its London-based spies met the future Labour leader and described him as a "very, very good source".
Mr Corbyn denies knowingly meeting any spies during the Cold War or passing information to them.
And the East German spy agency the Stasi kept a file on Labour Action For Peace at a time when Mr Corbyn was its vice-chairman in the hope that its agents could infiltrate the group and influence defence policy.