I'll be mailing in my taxes in the next few days as I need to apply for a ITIN using form W-7, however my passport as proof of identity expires in 3 weeks. Issue? thx

See this section of the Instructions for Form W-7.  The document you provide must be current.  If you can apply in person at a local IRS Taxpayer Assistance Center (TAC) or Certifying Acceptance Agent (CAA), that would be the best way to ensure that your application is not rejected for an expired document. 

TAC appointments typically can be scheduled by calling 844-545-5640.  See IRS.gov/W7DocumentVerification for a list of designated TACs that offer ITIN document authentication service.  The IRS website at this link can be used to find Certifying Acceptance Agents nearest to you.

Also, that same link to the instructions for Form W-7 provides a list of other documents that can be used for identification purposes.