Gilbert Moreno appeals his convictions for possession of cocaine with intent to distribute and conspiracy, 21 U.S.C. §§ 841(a)(1) and 846 (1982). Moreno was arrested when officers executing a search warrant at his home discovered cocaine and drug paraphernalia. He sought suppression of the seized cocaine and drug paraphernalia contending that the officers who executed the warrant had violated the "knock and notice" requirement of 18 U.S.C. § 3109 (1982).