N.Y. C.P.L.R. 1011

Rule 1011. Successive third-party proceedings; counterclaims. A\nthird-party defendant may proceed pursuant to section 1007 against any\nperson who is or may be liable to him for all or part of the third-party\nclaim. When a counterclaim is asserted against a plaintiff, he may\nproceed pursuant to section 1007 as if he were a defendant.\n