BP delay new oil cap testing

Crucial tests on a new device to cap the ruptured oil well in the Gulf of Mexico have been delayed.

BP is postponing the test to establish whether the well can withstand the pressure caused by closing the cap on top of the ruptured wellhead.

"We decided that the process may benefit from additional analysis that will be performed tonight and tomorrow," retired Coast Guard Admiral Thad Allen, who is overseeing the US response to the spill, said in a statement.

The test, due to last between six and 48 hours, was originally scheduled for late Tuesday on BP's newly installed "capping stack," which has a better seal than the last cap placed on the well and aims to stop oil from spewing out of the failed blowout preventer.

Regardless of the test results, BP should be able to contain the blown-out well's flow with oil-siphoning vessels by mid-July, Allen said earlier.

The only proven way to permanently kill the leak lies in the drilling of relief wells to intercept the ruptured one.

The first of two such wells started in May is expected to intercept it by the end of July and plug it with drilling mud and cement by mid-August.