You should consider potential use of Acquisition and Cross Servicing Agreements (ACSAs). You might have circumstances where ACSA use may solve your problems. ACSA use has specific rules and this alternative to a contract is not necessarily a short-cut.

As with any acquisition method, ACSAs involve specific administrative processes and the added dimension of bilateral agreements (sometimes more complicated than an FMS Case), so you will need to carefully weigh the risk and circumstances before selecting either a US awarded contract or careful use of an ACSA.

Here are resources to get you started:

https://www.acq.osd.mil/ic/acsa.html

https://www.dau.edu/cop/iam/Pages/Topics/ACSA.aspx