President Barack Obama says the U.S. is taking steps to enhance the safety of air travel, including beefing up cargo screening.
Authorities are taking the steps after two packages of explosives were intercepted overseas, headed from Yemen for Jewish places of worship in Chicago.
Obama told reporters Friday that he was alerted to the threat Thursday night and that he directed the Homeland Security Department and other law enforcement and intelligence agencies to take whatever steps were necessary to protect American citizens.
He said additional protective measures will be taken for as long as necessary to ensure safety and security in this country.
Officials suspect a link with al-Qaida.