Oil headed for the biggest weekly gain in more than four years amid signs a slowing in U.S. production may trim the biggest supply glut since 1930. Futures were little changed in New York and poised for a 9.6 percent advance through April 17, the most since February 2011. Crude output dropped last week while supply from shale formations is forecast to decline in May, according to the Energy Information Administration. The U.S. Senate reached an agreement on the path forward for a bill on Iran that may give lawmakers a chance to review a deal on its nuclear program. Oil has rebounded about 30 percent from a six-year low in March amid signs the idling of drill rigs in the U.S. is spurring a production slowdown that may ease the surplus. The rally may still falter as crude stockpiles continue to expand to the highest level in 85 years. West Texas Intermediate for May delivery was at $56.61 a barrel in electronic trading on the New York Mercantile Exchange, down 10 cents at 9:04 a.m. Sydney time. The contract rose 32 cents to $56.71 on Thursday. The volume of all futures traded was about 91 percent below the 100-day average. Brent for June settlement gained 66 cents, or 1 percent, to $63.98 a barrel on the London-based ICE Futures Europe exchange on Thursday. The European benchmark crude ended the session at a premium of $5.87 to WTI for the same month. Source: Bloomberg