Why didn't Toyotomi send Tokugawa troops to China orKorea?

Nov 2013
It seems to me as if Toyotomi should have either sent Tokugawa or his troops to China; either in support of his invasion or to drain the Tokugawa clan of it's strength. Instead Tokugawa is simply able to refuse participation in the Imjin war altogether, if I am not mistaken.

Why didn't Toyotomi dispatch either Tokugawa, or at least more of his resources in support of the Imjin war?