BP PLC has taken new steps to bolster its cash and available credit, adding $5 billion to its oil-spill war chest amid deepening concerns about the escalating costs of the Gulf of Mexico disaster.

A person familiar with the matter said BP had arranged more than $3 billion in new unsecured bank credit lines in the past week and had picked up $2 billion in cash borrowed against BP's stake in OAO Rosneft, the state-controlled Russian oil firm, and other assets.

BP's total cash and available credit now tops $20 billion, up from the $15 billion that BP said it had on June 16.

BP has lost roughly $100 billion in market value since a drilling rig it had been leasing, the Deepwater Horizon, exploded in the Gulf of Mexico in late April, unleashing what could prove to be the worst oil spill in U.S. history. Credit-rating agencies have downgraded its debt to near junk status.

Details of the additional funding were reported online Friday by The Wall Street Journal as BP's share price fell to its lowest level in 14 years. The shares were off 6%, or $1.72, at $27.02 in 4 p.m. trading on the New York Stock Exchange.

Fears have been escalating that the cost of the spill will be greater than expected, and some analysts have speculated the toll could lead to a bankruptcy filing.

BP dismisses such speculation and says it has ample resources to ride out the crisis. It has boosted the bill for its response so far to $2.35 billion, including the cost of the clean-up, containment, drilling of relief wells, grants to U.S. states and compensation claims paid. It is unclear what the ultimate cost of the spill will be for BP and whether the steps the company has already taken to shore up its balance sheet will be enough.

Market jitters were reinforced by concerns Friday that a potentialtropical storm in the Caribbean Sea may head towards the Gulf, potentially hampering BP's effort to contain the spill. There are some 30,000 people, more than 4,500 ships and some 100 aircraft involved in the clean-up and logistics.

BP has several options for asset sales, said bankers familiar with the matter. High on its list would be its 60% stake in Argentine oil and gas producer Pan American Energy, and assets in Colombia and Venezuela.

Or BP may reduce its stakes in U.S. fields operated by partners, such as the Gulf field Mars, operated by Royal Dutch Shell PLC.

Energy analysts believe that with the Deepwater Horizon disaster harming its brand in America, BP could be keen to sell U.S. assets.

'BP needs to downsize its exposure to the U.S. due to the political risk they face there now,' said Jason Kenney, an analyst at ING Bank. He expects BP will seek to reduce its position in U.S. onshore natural gas or in mature oil fields outside of Alaska.

One possibility that doesn't appear imminent is a takeover of the whole company.

Though speculation has swirled in recent weeks that a rival such as Exxon Mobil Corp. could swoop in and take advantage of BP's weakened state, several bankers say such a move is unlikely at least until the extent of its spill-related liabilities become clear.

A person familiar with the matter said BP has received no takeover approaches in the wake of the spill.

Last week, BP acceded to White House demands to set up a $20 billion escrow account for compensating victims of the oil disaster.

It said it would offset the cost of the remediation fund by canceling its dividend for three quarters, raising $10 billion from asset sales and cutting capital spending.

'As we announced last week, our board considers it appropriate in the circumstances to maintain a very conservativefinancial position, with a focus on conserving cash,' BP spokesman Andrew Gowers said.

Yields on the company's bonds soared Friday, as did the cost of insuring its debt. The cost of protecting $10 million-worth of BP bonds against default rose by $44,000 a year to $580,000.

Investors' fears were stoked by a report by Nomura Holdings Inc. in London saying BP may need to sell shares to assure trading partners it has the financial wherewithal to absorb costs related to the spill.

Nomura analyst Alastair Syme said while BP has enough liquidity to deal with the clean-up costs and the phased funding of the escrow account, it may struggle if liabilities from the spill were to rise, for example due to hurricane damage, or if oil prices fall. He said BP's options are constrained because issuing debt has become expensive and selling off assets takes time.

Mr. Syme said BP has an estimated '$2 billion to $2.5 billion of one-year commercial paper to roll over, needed to fund day-to-day trading activities and working capital, which will likely be much harder (and more expensive) to do in this environment.' BP said it doesn't comment on its financial arrangements.

BP and its advisers had been considering a large bond sale to shore up the company's finances, but have shelved the plan for now, other people familiar with the matter said.

Nomura's Mr. Syme wrote that BP could raise equity-linked financing in the near term, perhaps from a Sovereign Wealth Fund. However, doing so at its depressed share price might make current shareholders uneasy, since they could face large dilution. One of those people familiar with the matter said BP has no imminent plans for an equity or bond deal.

In the last week or so, BP has arranged a so-called cap-and-collar deal with Credit Suisse Group, enabling the oil company to borrow funds backed by the Rosneft stake.

One of those people said that the proceeds from the Rosneft deal were less than $1 billion but that the company had struck other, similar deals.