U.S. President Barack Obama and U.K. Prime Minister David Cameron have agreed to keep open discussions about a possible release of oil held in emergency stockpiles, which have been used in the past to reduce prices or compensate for a supply disruption, a U.K. official familiar with the talks said Thursday. Mr. Cameron and Mr. Obama discussed the topic during a meeting at the White House Wednesday, but didn't come to any conclusions, the official said. The meeting came as oil prices remain very high and the International Energy Agency warned that sanctions against Iran could remove as much as 1 million barrels a day of oil production from an already tight market. Western powers will impose the strictest sanctions yet on Iran this summer, to pressure the country over its nuclear program. The European Union has agreed to ban all imports of oil from Iran from July 1, and both the EU and the U.S. will tightly restrict transactions with Iran's central bank, further constricting th...