By Stephanie Kelly and Muyu Xu (Reuters) – Oil benchmarks were headed for a seventh straight weekly decline on worries over a global supply surplus and weak Chinese demand, although prices recovered ground on Friday after Saudi Arabia and Russia called for more OPEC+ members to join output cuts. Brent crude futures rose $1.54, or 2.1%, to $75.59 a barrel by 0704 GMT, while U.S. West Texas Intermediate crude futures gained $1.39, or 2%, to $70.73 a barrel. Both benchmarks slid to their lowest since late June in the previous session, a sign that many traders believe the market is oversupplied. B…