The Israeli air force says it will only evaluate a US offer to sell it surplus Boeing KC-135 tankers if the aircraft involved are R-model examples.
Washington has so far only proposed the sale of three KC-135Es, worth around $200 million.
Israeli sources say the air force has made it clear it prefers the CFM56-powered R-model aircraft. These are included in the USA's excess defense articles programme, which allows Washington to give its allies military hardware for free, or at a greatly reduced price.
The Israeli service is looking for new tankers, and surplus KC-135s were included in a US offer of equipment several months ago, which also featured the Bell-Boeing V-22 tiltrotor.
Israeli sources say that if the USA agrees to supply the longer-range KC-135R a deal could include 12 examples, to be transferred after undergoing depot maintenance in the USA.
The air force intends to use two of the aircraft for VIP transport applications, the sources add.
The Israeli government has for some years evaluated options for an "Air Force One"-type capability to conduct missions such as flying the nation's prime minister to foreign countries. An earlier programme was shelved following a request for information process, however, due to its price.
No official response has been given to the status of the negotiations.
The Israeli air force is currently using a fleet of upgraded Boeing 707 in-flight refuelling tankers, which were converted by Israel Aerospace Industries. These continue to be modified, with recent enhancements having introduced a new glass cockpit, modern communications equipment, a global air traffic management system and the same type of refuelling boom used by the US Air Force's KC-135s.