Documents published Monday by The Intercept revealed the "far-reaching" extent of the U.S. National Security Agency's collaboration with Israeli intelligence services. The revelations came as the U.S. State Department criticized Israel for its "disgraceful" shelling of a U.N. school, and the death toll in the Israeli offensive in Gaza surpassed 1,800 Palestinians and 60 Israelis.

The documents, some from as recently as 2013, show that under agreements with the Israelis, the U.S. has provided cash, raw data and analysis, much of it directed against "Palestinian terrorism."

The Intercept's Glenn Greenwald wrote that the documents "underscore the indispensable, direct involvement of the U.S. government and its key allies in Israeli aggression against its neighbors. That covert support is squarely at odds with the posture of helpless detachment typically adopted by Obama officials and their supporters."

Several of the documents published center on the assistance the NSA provides to the Israeli SIGINT National Unit, the secretive signals intelligence organization also known as Unit 8200. The Israelis work together with the U.S., Britain and Canada to collect signals from throughout the Middle East.

An April 13, 2013, NSA document says that the agency "maintains a far-reaching technical and analytic relationship with the Israeli SIGINT National Unit (ISNU) sharing information on access, intercept, targeting, language, analysis and reporting."

While the documents don't show any instances of U.S. intelligence agents identifying Palestinian targets for Israeli forces to strike, the U.S. has provided similar services in the past, such as for Iraq in its war against Iran.

One of the most intriguing documents suggests that in 2003 and 2004, the U.S. explored a "massively expanded intelligence-sharing relationship called 'Gladiator.'" But the Israelis demanded hundreds of millions of dollars in exchange for the project, which "appears never to have been consummated." However, the documents do show receipts for $500,000 cash payments to Israel; it is unclear if the receipts represent one or multiple payments, and their exact purpose is undocumented.

A Sunday report in Der Spiegel emphasized the often-conflicted relationship between the American and Israeli spying apparatuses. The report claimed that Israelis intercepted the telephone conversations of Secretary of State John Kerry during peace negotiations last year. A previous Greenwald article, also based on documents from former NSA contractor Edward Snowden, showed that an intelligence estimate found the Israelis were the third-most aggressive intelligence service in spying on the U.S.