Israel has given retired US-supplied Cobra combat helicopters to Jordan to help the Hashemite kingdom fend off insurgent threats on the Syrian and Iraqi borders, a US official with knowledge of the deal said.The handover, initiated last year, was approved by Washington, which provided mechanical overhauls for the aircraft before they were incorporated free of charge in Jordan's existing Cobra fleet, the official said."These choppers are for border security," the official, who requested anonymity due to the sensitivity of the issue, told Reuters. Asked how many Cobras were transferred, the official said: "Around 16, though some may have been used by the Jordanians for spare parts" rather than kept intact.Jordanian and Israeli officials declined comment, as did the Pentagon.Israel and Jordan, as well as Saudi Arabia and Iraq, this week hosted US Defense Secretary Ash Carter, who offered reassurances about the regional fight against Islamic State and the July 14 international deal curbing Iran's nuclear program.Israel originally had two Cobra squadrons - each consisting of around 30 of the aircraft, which are designed to back ground troops with aerial surveillance as well as machine gun and rocket fire, and to be nimble enough to elude surface-to-air missiles. One of the squadrons was disbanded in the mid-2000s and the other in 2013, with Israel's air force preferring the more powerful, US-supplied Apache helicopters also in its fleet and an expanded role for its thrifty and versatile pilotless drones.The Jordanian air force has 25 Cobras in service, according to the London-based International Institute for Strategic Studies. The Cobra's manufacturer is Bell Helicopter, a Textron company.Following Egypt, Jordan made peace with Israel in 1994. But the countries had maintained discreet security ties dating back to the early 1970s and Israel has pledged to step in should Amman be threatened by Islamic State or other insurgents rampaging elsewhere in the Middle East.