H1B Transfer - Client letter for only 6 months

H1B Transfer from Company A to Company B on regular processing. Got RFE for client letter. Client is ready to give the letter but he is mentioned that project duration is only 6 months. I am not able to convenince client to provide more than that. Can i submit this client letter for my RFE? If yes, will there be any issue.

Ask the client if they can add some text which says that although the project is for 6 months, but there is a possibility of further extension in future. That would help.

Else, you can submit whatever best you can receive from them. It will be then USCIS officer’s discretion whether to approve it for the term of the project or for 3 years (assuming that’s what your employer requested).