BP shares plunged more than nine percent on Monday as investors fretted over the spiralling cost of the Gulf Mexico oil spill crisis and the future of the group's shareholder dividend.

BP's share price tumbled to 355 pence amid mounting pressure from US President Barack Obama over the group's handling of the worst-ever environmental disaster in US history.

Visiting spill-hit areas, Obama said he hoped for an outline deal with BP by Wednesday on a multi-billion dollar fund for oil disaster victims, and vowed to use all his power to heal the Gulf coast.

"My hope is that by the time the (BP) chairman and I meet on Wednesday that we've made sufficient progress that we can start actually seeing a structure that would be in place," he said at a staging post for oil clean-up efforts.

BP directors earlier met in London to discuss the cost of sorting out the disaster, which had jumped to about 1.6 billion dollars (1.3 billion euros), and whether to suspend a dividend payment to shareholders.

Reports have suggested that BP will bow to massive US pressure and decide to suspend the payments as its potential liability over the oil spill soars.

"Some investment firms are fearing that the dividend will be scrapped," said Rajesh Patel, head trader at financial betting firm Spread Co.

"BP's board are discussing what to do with their dividend this afternoon and it is a massively important decision for investors whatever they decide," Patel said.

"It looks though like some (investors) have decided that enough is enough with BP."

A BP spokesman told AFP that no formal announcement on the dividend was due on Monday.

New York-listed BP shares also fell heavily, ending the day down 9.7 percent.

Ahead of the board meeting, BP said that "the cost of the response to date amounts to approximately 1.6 billion dollars, including the cost of the spill response, containment, relief well drilling, grants to the Gulf states, claims paid, and federal costs."

The figure is up from an estimated 1.43 billion dollars announced by BP on Thursday. BP's market value has fallen by tens of billions of dollars as its share price plunged after the BP-operated Deepwater Horizon rig sank on April 22.

The accident, following an explosion that killed 11 people two days earlier, sparked an enormous spill from a leaking well on the sea bed, with huge amounts of oil washing up on the US Gulf coastline, threatening precious wildlife and local communities.

BP said in Monday's statement that "work continues to collect and disperse oil that has reached the surface of the sea, to protect the shoreline of the Gulf of Mexico, and to collect and clean up any oil that has reached shore."

US Coast Guard Admiral Thad Allen, in charge of the US response to the Gulf oil spill disaster, said Sunday that he expected BP chief executive Tony Hayward to attend a White House crisis meeting due Wednesday.

Allen said issues at the top of the agenda would include oil spill containment options and the claims process for victims.

Obama's political opponents have piled criticism on the president for his failure to so far meet, or talk by telephone with Hayward, who has become the public face of the disaster for BP.