U.S. producers battling OPEC for market share may increase output further from the highest rate in more than three decades as costs decline almost as fast as oil prices, according to Goldman Sachs Group Inc.

The slump in benchmark U.S. crude futures, which are down more than 40% this year, is driving producers to move drill rigs to lower-cost fields, the bank said in an emailed report. While there’s evidence of some rebalancing starting to occur in the market, that isn’t sufficient, it said.

An OPEC decision in November to maintain its output target prompted speculation that the group is willing to let crude slide to a level that would slow U.S. production. Smaller member-nations including Venezuela, which have called for action to support prices, may play a role in rebalancing the market, Goldman said.

“Costs are falling nearly as fast as the price, which means oil producers can spend less to get the same or potentially even more in terms of production,” the bank said. “While reductions in capex are coming faster than expected, it is unlikely to translate into less supply” it said, adding that drill-rig rates have dropped as much as 20%.

ConocoPhillips, the third-largest U.S. energy producer, cut its capital expenditure by about 20% for next year amid the price slump driven by horizontal drilling and hydraulic fracturing that have opened up shale formations.