LONDON, July 18 (Reuters) - Under-fire oil company BP Plc BP.L has started canvassing shareholders about a restructuring in the wake of its Gulf of Mexico oil spill which could include a break up of the business, the Sunday Times reported.

The newspaper, citing unnamed BP insiders, said options included selling the group’s refineries and petrol stations, scaling back its U.S. operations and ramping-up in-house engineering instead of outsourcing.

These are on top of the sale of about 10 percent of its assets, including its stake in the giant Prudhoe Bay field in Alaska, the Sunday Times added.

A BP spokesman said it did not comment on rumour and speculation.

BP, which has already divested much of its downstream operations in recent years, said last month it planned to sell around $10 billion of assets to help pay for costs from the worst offshore oil spill in U.S. history, but declined to say which assets were up for grabs. [ID:nLDE66C0N7] [ID:nN12148109]

On Saturday, the oil group extended for another 24 hours a critical test of its blown-out Gulf of Mexico well that has so far shut off the huge oil leak, a top U.S. official overseeing the spill response said. [ID:nN17152937] (Reporting by Mark Potter; Editing by David Holmes)