Domain Trust

Domain A (WinNT4.0); Domain B (W2K); Domain C (W2K).

Domain A trust B and B trust A.
Domain B trust C and C trust B.
I cannot establish trust between Domain A and C.

From domain C I can use usermanager and assign users of domain A to groupsof domain C; but I cannot do the same from domain A.

How can I resolve this?