British oil giant BP on Friday began pumping cement into its damaged well in the Gulf of Mexico to seal the undersea gusher for good.

Photo taken on Sept. 4, 2010 and released on Sept. 5 show the damaged Blow Out Preventer (BOP) from the Deepwater Horizon oil rig being pull out by the Q4000 vessel in the Gulf of Mexico. [Xinhua]

The cement-pumping began at 1:30 p.m. local time Friday and will take a few hours to complete, a BP spokesman was quoted by U. S. media as saying.

BP said earlier Friday it will permanently seal the ruptured oil well in the Gulf of Mexico on Saturday.

A relief well intersected the blown-out well on Thursday, paving the way to pump in cement in a "bottom kill" operation on the well that caused the worst spill in U.S. history, the company said.

"It is expected that the MC252 well will be completely sealed on Saturday," it said.

"Once cementing operations are complete, the DD3 will begin standard plugging and abandonment procedures for the relief well," it said.

BP plugged the damaged oil well with cement last month. But the relief wells are believed to be the most secure way to seal the well for good.

After the April 20 blast on BP-leased Deepwater Horizon rig opened the gusher about 1.6 km under the Gulf of Mexico, hundreds of millions of liters of crude oil spewed into the sea before BP sealed the leak in mid-July with a tight-fitting containment cap.