LONDON—BP PLC on Tuesday swung to a loss in the second quarter, as earnings were hit by lower oil prices and a multibillion-dollar charge relating to the deal it reached earlier this month to settle U.S. federal and state claims over the 2010 Deepwater Horizon disaster.

London-based BP said its replacement cost loss—a number analogous to the net income that U.S. oil companies report—was $6.27 billion, compared with a profit of $3.18 billion a year earlier.

The sharp decline reflects a $10 billion pretax charge that BP recorded as part of an $18.7 billion agreement with the U.S. government and five states to settle legal claims relating to its fatal oil spill in the Gulf of Mexico. The earnings also reflect a quarter in which oil prices rebounded off lows hit in January, but remained well below year-ago levels.

The slide in oil prices creates a challenging environment for BP as it prepares to finally move on from the Deepwater Horizon disaster. The last five years have taken their toll on the company, which sold off more than $40 billion in assets to raise cash for cleanup and legal costs. While the settlement will give the company more room to maneuver, the weak oil price will keep the pressure on.

The company has already announced plans to cut spending in response to lower prices and organic capital expenditure fell to $4.5 billion in the second quarter. Organic capital expenditure for the whole year is now expected to be below $20 billion.

"The external environment remains challenging, but BP moved quickly in response and we continue to do," said CEO Bob Dudley. "I am confident that positioning BP for a period of weaker prices is the right course to take, and will serve the company well for the future."

Write to Sarah Kent at sarah.kent@wsj.com

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