U.S. shale-oil drillers, who aren't a part of the output agreement, have been cited as the main culprit, disrupting OPEC's efforts to stabilize oil prices.
Prices went lower on new signs of rising output from Nigeria and Libya, the two OPEC members exempt from a deal to cut production.
The market is turning lower in part on tanker-tracking data showing unsold crude oil cargoes from Nigeria, he said. U.S. production is also a concern because American drillers locked in prices for future delivery, and so they'll keep pumping even as near-term prices fall, according to Kilduff.
The market has been waiting for signs that OPEC's strategy is achieving its stated goal: driving global crude stockpiles down to the five-year average. Last week, the International Energy Agency warned inventories might not fall to that level until close to the expiration of OPEC's current deal in March.