What conflict resolution technique is a project manager using when he says, "I cannot deal with this issue now!

This is Withdrawal or avoiding technique.

Some examples where this could be used

• When the issue is trivial and not worth the effort
• When more important issues are pressing, and you don't have time to deal with it
• In situations where postponing the response is beneficial to you, for example -
  • When it is not the right time or place to confront the issue
  • When you need time to think and collect information before you act (e.g. if you are unprepared or taken by surprise)
• When you see no chance of getting your concerns met or you would have to put forth unreasonable efforts
• When you are unable to handle the conflict (e.g. if you are too emotionally involved or others can handle it better

This is WITHDRAWAL type of conflict resolution.