David Evans, Welsh secretary of the National Union of Teachers Cymru, said a satisfactory deal was still being thrashed out at four Welsh schools locked in continuing disputes over the payments. But he warned strike action was imminent, especially at a school where more concessions are being sought in crisis meetings next week.
Strikes at two of Swansea's comprehensive schools, Gowerton and Cefn Hengoed, have already taken place over two days in July. Sources say members at one of the schools are still unhappy over concessions offered.
Negotiations are also continuing at Ebbw Vale in Blaenau Gwent and Pontllanfraith in Blackwood, Gwent.
Pay and conditions are not devolved to Wales, making it a border-crossing issue. Members are angry over the introduction and distribution of new teaching and learning responsibilities (TLRs), which replaced the old management allowances in January. Some members on the old allowances could lose up to pound;5,600 a year.
Welsh heads were allowed three extra months to revise their staffing plans, which meant they did not have to be officially in place until March 1 this year.
Strikes are planned at five schools in England next week and staff at a total of 42 schools across England and Wales have now walked out over the changes. Mr Evans, from the NUT Cymru, said the union had put forward alternative staffing structures over the summer but they had not been accepted.