I believe it was a politically risky statement for him to make explicitly.
If he alienates his Right Wing, they could dismantle the government and force elections at will. In the past he has used vague statements or diversions to avoid making public statements that could pose political risks to him. No one was demanding an answer on the issue (and he left out plenty of issues that US lawmakers HAVE demanded to know about).
The better question is: Why would he take the risk of saying it at all?