A four-hour "range countdown" for test-firing of India's 3,000 km intermediate range ballistic missile Agni III from the launch pad at the Wheeler's Island in Balasore began at six am on Thursday morning, defence sources said.
The missile was likely to be fired before noon, the sources indicated.
DRDO scientists were busy providing final touches to the missile which was test-launched unsuccessfully on July nine last year.
The range countdown can be put on hold if any snag was found in the missile and commence again after the same was rectified, the sources explained.
According to the sources, three minutes before the blast-off, there would be a hold in the range countdown process and an "auto launch sequence" would take over so that a network of computers in the main control station could check all the health parameters of the missile as well as its sub-systems and allow the missile to move forward in the pre-programmed trajectory.
Air Traffic Controls at Kalaikunda base, the Airports Authority of India at Kolkata and Eastern Naval Command at Visakhapatnam had been intimated about the test firing of the missile.
The administration in the coastal districts of Balasore, Bhadrak and Kendrapara have also been intimated to warn fishermen not to venture into the sea during the launch period, the sources said.