Is it ok to receive it by fax?

[vikasintl]

I am applying for visitors' visa to USA.

My sponsor sent me affidavit of support by courier but forgot to send invitation letter and letter to consulate by fax so I want to know if it is ok to receive invitation letter and letter to consulate by fax? and carry fax print at time of interview(as I will get fax as an email attachment which I can print)

My interview date is fixed and now time is not enough to send both these letter by fax?
Is it compulsory to get invitation and letter to consulate by courier only?if so do I reschedule my interview date?

[knowledgeable]

Yes

.