NASA said its sky observation from Arizona discovered the objects on September 5. One asteroid was believed to be 10 to 20 meters (32 to 65 feet) in size and was expected to pass within 248,000 kilometers (154,000 miles) of Earth at 0951 GMT.

The second object estimated to be six to 14 meters (20 to 45 feet) in size was set to pass within 79,000 kilometers (49,000 mile) 2112 GMT.

"Both objects should be observable near closest approach with moderate sized amateur telescopes," NASA said. "Although neither of these object has a chance of hitting Earth, a 10 meter-sized near-Earth asteroid from the undiscovered population of about 50 million would be expected to pass almost daily within a lunar distance, and one might strike Earth's atmosphere about every 10 years on average." NASA estimates that asteroids smaller that 25 meters in diameter would burn up while entering the atmosphere, and cause no damage.