Johannesburg - Workers in the coal sector will go on strike following failed wage negotiations, the National Union of Mineworkers (NUM) said on Wednesday."We have deadlocked. We have received a strike certificate and we are going on strike," spokesperson Lesiba Seshoka said.On Thursday, the NUM would give employers the necessary 48-hours notice of the strike and would discuss the date of the strike with its 150 000 members in the coal sector, he said."We will definitely serve notice tomorrow, there is no question about it."Seshoka said the talks deadlocked after employers offered a final wage increase of seven percent. The union was demanding 14%."We cannot accept that. We have totally rejected it because that is not according to our mandate," he said.The only way to increase the wage offer was to have a "powerful strike"."A powerful strike is a strike that lasts more than a week. It must take many weeks for a strike to work with as much members as possible."The NUM, the United Association of SA (Uasa) and Solidarity rejected an offer by the Chamber of Mines last Monday.It was not known if Uasa and Solidarity also intend striking.The Chamber represents Anglo Thermal Coal SA, Delmas Coal, Exxaro Resources [JSE:EXX], Kangra Coal, Optimum Coal and Xstrata Coal.The negotiations are being mediated by the Commission for Conciliation, Mediation and Arbitration (CCMA).In a statement, chamber spokesperson Jabu Maphalala confirmed the deadlock.He said the coal mining companies had tabled a final offer of an 8.5% increase for entry level employees and seven percent for other employees.Delmas Coal had offered 7.5% for entry level workers and six percent for the rest, he said."The wage offer should be seen in conjunction with other offers already made, which include medical incapacity and medical aid contributions as well as the living out allowance," Maphalala said.Frans Barker, a negotiator for the coal mining companies, said the unions had jointly submitted more than 50 demands."However, they declared a dispute after only two negotiating sessions and deadlocked after a single meeting under the auspices of the CCMA."The negotiations were thus not given a fair chance to succeed," he said.The companies were "deeply disappointed" at the "untimely declaration" of deadlock."The companies have also clearly indicated to the unions that they were more than willing to continue to engage on the many demands in an attempt to reach settlement, however the unions rejected this," Barker said.