The US routinely attempts to gather information on Israel's alleged atomic arsenal and secret government deliberations, according to new official documentation on Israel's intelligence services reviewed by Reuters. While spying on allies is not uncommon, a new Israeli state-sponsored publication openly acknowledges it. The author of the book, Masterpiece: An Inside Look at Sixty Years of Israeli Intelligence, claims American spy agencies use technologies like electronic eavesdropping, and specially trained staff located in the US embassy in Tel Aviv, for "methodical intelligence gathering." "The United States has been after Israel's nonconventional capabilities and what goes on at the decision-making echelons," according to a chapter on counterespionage written by Barak Ben-Zur, a retired Shin Bet (Israel Security Agency) officer. Asked about the assertions, the US Embassy spokesman said only: "We don't comment on intelligence matters." Israel is widely believed to have had nuclear weapons since the late 1960s, but a policy of "strategic ambiguity" has prevented state officials in the know from confirming or denying the claims. Declassified Pentagon documents published in a 2004 book about then-US defense secretary Donald Rumsfeld estimated that Israel had 80 nuclear warheads. Last May, former US president Jimmy Carter put the number of Israeli bombs at around 150. The estimates on Israel's nuclear arsenal range from about 80 to more than 200, as do estimates on its delivery capabilities, which apart from ballistic missiles may or may not include custom-designed torpedoes. Ben-Zur declined to give Reuters operational details on how the United States might be conducting its espionage on Israel. But he described the effort as largely benign, given the closeness of defense ties between Israel and Washington. "At the end of the day, the United States does not want to be surprised," he said. "Even by us." Due out later this month, Masterpiece is published by the Israel Intelligence Heritage and Commemoration Center and includes prefaces by chiefs of Military Intelligence, the Shin Bet and the Mossad.