BP has begun work on a relief well that could be used to plug the massive oil leak in the gulf coast. The new drill site is about half a mile on the seabed from the leaking well beneath the Gulf of Mexico, and drilling is estimated to take some three months.

The company began work on the well early Sunday afternoon, but only announced that work had been begun Tuesday morning. The relief well also in 5,000 feet of water beneath the Gulf of Mexico, is planned to intercept the existing well around 13,000 feet below the seabed and permanently seal it.

A relief well is designed to intersect an existing well bore and pump heavy fluids and cement in to stop the leaking oil. BP has described it as the only way to definitively plug the oil leak.

"This is another key step in our work to permanently stop the loss of oil from the well," BP Group chief executive officer Tony Hayward said in a statement.

The well is being drilled by the ultra-deepwater semisubmersible rig Development Drill III, owned and operated by Transocean, the world's largest offshore drilling company.

While waiting for the relief well to be completed, response crews have been testing a new technique to break up the oil before it reaches the surface -- a remotely operated underwater vehicle dispensing sub-surface dispersant at a rate of nine gallons per minute -- with encouraging results so far.

According to a joint statement by BP, the NOAA and other government officials, nearly 3,000 gallons of subsea dispersants have already been applied, and scientists are monitoring the results to determine the feasibility of their continued use.