Najibullah Zazi's (nah-jee-BOO'-lah ZAH'-zee) lawyer entered the plea Tuesday in Brooklyn. Zazi was ordered held without bail during the brief hearing.
Defense attorney J. Michael Dowling says what he's seen so far "does not amount to a conspiracy."
He says he doesn't know the names of anyone accused of conspiring with his client.
Officials say the 24-year-old Zazi and his co-conspirators bought beauty products in Colorado containing key ingredients for homemade bombs.
Prosecutors believe Zazi received explosives training from al-Qaida in Pakistan and planned to target mass transit in the New York City area.