By Andrea Shalal and Idrees Ali
North Korea's recently launched satellite is once again tumbling in orbit, after stabilising briefly, according to a US official and other sources.
The satellite update came as a key US congressional watchdog agency said the military had not demonstrated its ability to protect the US against a possible North Korea missile attack.
Earlier this month, North Korea launched what it said was an earth observation satellite but what the country's neighbours and the US called a missile test.
It was earlier believed to have achieved stable orbit but not to have transmitted data back to Earth.
The US official, and two other sources with knowledge of the issue, said they are less concerned about the function of the satellite than with the technology involved in launching it.
They added that the launch was clearly intended to demonstrate North Korea's ability to launch an intercontinental ballistic missile.
The US Government Accountability Office (GAO), the research arm of Congress, highlighted concerns about missile attacks from North Korea in a report released on Wednesday (local time).
"GMD flight testing, to date, was insufficient to demonstrate that an operationally useful defence capability exists," the GAO said.
GMD is an acronym for a ground-based missile defence system.
The report said the missile defence system, or the Ground-based Midcourse Defense, had only demonstrated "a partial capability against small numbers of simple ballistic missile threats".
Ken Todorov, former deputy director of the Missile Defense Agency, said the organisation faced a difficult balancing act in meeting the needs of the US military and operating with limited resources for testing.