BP is the UK's largest oil company
Lower oil prices in the global downturn have led to second-quarter profits at BP more than halving from a year ago.
Its replacement cost profit between April and June was $3.1bn (£1.9bn), down 53% from $6.75bn a year earlier.
Oil prices have hovered at between $60 and $70 a barrel recently - well off the high of $147 seen last July, but up from the $30 lows of earlier this year.
Chief executive Tony Hayward said the firm expected the global economic recovery to be "long and drawn out".
'We are in turbulent times, volatile and uncertain. But we continue to steer a steady course through choppy waters," he added.
The results took BP's half-year profits to $5.5bn, down 57% from the first six months of 2008.
However, its second-quarter profit was up 30% from the first three months of the year.
Daily production rose by 4% in the three months to the end of June, BP said.
REPLACEMENT COST PROFIT
Replacement cost profit is the reporting measure typically used by oil companies and reflects the current cost of supplies
The measure strips out gains or losses related to any changes in the value of the firm's stock of fuel products
This figure is being closely monitored by analysts to see how output cuts by oil producer cartel Opec and attacks by militants in Nigeria have hit growth in the sector as a whole.
BP said that it had already achieved the $2bn in cost-cutting it had aimed for in 2009, and was expecting to save a further $1bn during the rest of the year.
Last month, the company appointed Carl-Henric Svanberg, the Ericsson chief executive, as its new chairman to replace Sir Peter Sutherland.
Mr Svanberg is joining at a challenging time for the firm after almost 40% of investors voted against BP's remuneration report at its annual meeting.
BP's rivals, including Royal Dutch Shell, are set to report their results in the coming days. Richard Hunter of Hargreaves Lansdown Stockbrokers said BP had "thrown down the gauntlet to the rest of the oil supermajors".
"The reduction of the headline figure is of little surprise given the more recent lows which the oil price is experiencing," he said.
"Nonetheless, the company has been far from resting on its laurels given this backdrop."