A classified document leaked by National Security Agency whistleblower Edward Snowden reveals the intelligence cooperation of the US, UK and Israel regarding Iran.

The top-secret document, dated April 2013, focuses on the growing threat the Islamic Republic represents. It discusses trilateral cooperation between the NSA, GCHQ (Britain’s Government Communications Headquarters) and the ISNU, the IDF’s 8200 signal intelligence unit.

Like earlier documents leaked by Snowden, this one details the intelligence relationship between the countries involved. Specifically, it outlines the successes of the US and Britain in obtaining information on Iran, which is classified as a regional and cyber threat. It also expresses reluctance to formulate an overarching intelligence-sharing agreement with Israel.

“The trilateral relationship is limited to the topic of [redacted] and will serve as proof of concept of this kind of engagement,” the document reads.

The document was published in early February by The Intercept, a website set up by journalist Glenn Greenwald to publicize the leaked documents without being arrested, but according to the Jerusalem Post, the Israel-Iran angle got added attention.

Among the topics addressed by the document were “multiple high-priority surges” with GCHQ, including intelligence gathering surrounding the 2011 storming of the British Embassy in Tehran; the Iranian discovery of the computer virus meant to slow their nuclear efforts, known as FLAME; and “support to policy-makers” during nuclear negotiations between Iran and the P5+1 group of world powers.

“NSA has seen Iran further extending its influence across the Middle East over the last year,” the document warns. It cites Iran’s efforts to launch cyber-attacks on US targets as example.

Under the sub-heading “Potential Landmine”, the document indicated that Britain favored expanding cooperation with Israel, but the NSA signal chief was opposed. Previous revelations have exposed other cooperative efforts between Israel and the US, including Israeli intelligence studying metadata on behalf of the NSA which US law prevents the NSA from reviewing. Cases of the US eavesdropping on Israeli officials and vice versa were also publicized.