Decisions about whether Israel will select Boeing’s KC-46A tanker and ask for additional Lockheed Martin F-35s will depend on the result of current negotiations about the size of the US Foreign Military Funding (FMF) package that the nation will receive over the next 10 years.

Within the next few months, the allies are expected to agree the draft of a memorandum of understanding covering US funding to Israel’s military. Sources indicate that the Obama administration is likely to increase the FMF package by up to $1 billion for the decade to be covered in the new accord, which would set its contribution at about $4.1 billion a year.

Israeli officials have said within the past few days that even with this increase, the sum will not be enough to cover the defence needs of Israel following Iran’s nuclear agreement with the West.

With sufficient funding, the Israeli air force could select the KC-46A – which is now in advanced testing for the US Air Force and also on order for Japan – and abandon an alternative plan to purchase converted 767s.

The acquisition of additional F-35I “Adir” fighters is also a priority for the Israeli air force, which later this year will take delivery of its first of example out of a total currently requested of 33.