OPEC's deal to cut oil production is unlikely to result in a substantial reduction in actual supplies, some of the world's biggest oil trading companies said on Wednesday, meaning the market is unlikely to rebalance until well into 2017. The price of crude oil has stabilised around $50 a barrel since the Organization of the Petroleum Exporting Countries agreed the output deal on September 28, but rising production from Libya and Nigeria - both members of the producer group - casts doubt over the agreement's effectiveness, the heads of trading firms Gunvor and BB Energy told the Reuters Commodities Summit. "Clearly, they have put a floor on the market," Gunvor Chief Executive Torbjorn Tornqvist said. "But I don't think they can do any substantial cut. There are too many uncertain factors involved. These two countries (Libya and Nigeria) can wipe out any other deal that has been agreed." Any agreed reduction will not affect actual supplies until next year, Tornqvist added, because the next OPEC meeting to set supply policy, in Vienna on Nov. 30, will be too late to adjust cargo loading dates before 2017. "Realistically, they can't do anything till January. We're going to have quite a lot of oil in the market until then. I don't have high expectations of sustained higher oil prices, certainly for the medium term." 'WORK TO DO' Glencore's head of oil, Alex Beard, was also sceptical that OPEC's deal is a game changer. "We need to see the real deal in November rather than the talk of the idea of doing a deal," he said. "Libya's production is certainly going up at the moment and Nigeria is obviously off its lows as well. So I guess my outlook on the OPEC meeting is they've still got their work to do to come up with the detail that will convince the market." Gunvor's Tornqvist said the oil market is unlikely to rebalance until the middle or second half of 2017, giving a similar timeframe to that expected by Vitol's chief executive. Vitol CEO Ian Taylor on Monday said the price of oil in dollars could reach the high fifties to early sixties if OPEC and other producers cut supplies by 1 million barrels per day. "But can they really give us a million between OPEC and non-OPEC? It's a tough call," he said. The head of BB Energy, Mohamed Bassatne, told the summit on Wednesday that he does not expect a rapid rally or an early rebalancing of supply and demand. "I do think that the market will probably have found some kind of bottom between $45 and $50," he said. "It probably will go higher, but it still needs time to rebalance . I don't see it rebalancing until probably second half of 2017."