WASHINGTON—New U.S. intelligence shows Col. Moammar Gadhafi is "seriously considering" fleeing Tripoli for a more secure location outside the capital, according to U.S. officials, raising the prospect that the Libyan leader's hold on power is increasingly fragile.

The intelligence depicts a Libyan leader who "doesn't feel safe anymore" in Tripoli because of stepped-up strikes by North Atlantic Treaty Organization aircraft and by battlefield gains by rebel forces, according to...