GLASGOW, Nov 12 (Reuters) - Negotiators raced on Friday to find a deal establishing rules for global carbon offset markets as the UN climate summit in Scotland entered its final hours. The rules under Article 6 of the 2015 Paris Agreement would allow countries to meet their climate targets in part by purchasing offset credits representing emissions cuts by others.But negotiators are hung up on how to ensure multiple countries do not count the same credit toward their targets; whether to honour credits generated under an old UN system; and whether to tax trades to fund adaptation to climate change in poor countries. The latest draft for an Article 6 deal, published on Friday morning, showed little change on those three issues. In many cases, the text offered multiple, sometimes clashing, options for resolving them."The text tends to get messier before it gets tidied up so it"s not surprising you don"t see a lot of movement," said Kelley Kizzier, a vice president at the Environmental Defense Fund, who chaired the Article 6 talks at past U.N. summits. "The issues remain in there and the negotiations go on in the back room." Brazil and the United States have backed a Japanese compromise proposal on double counting offset credits. Under that proposal, the country that generates a credit would decide whether to authorise it for sale to other nations to count towards their climate targets. If authorised and sold, the seller country would add an emission unit to its national tally and the buyer country would deduct one, to ensure the emission cut was counted only once. Credits not authorised in this way could still be used in private markets, including by companies seeking to meet voluntary green goals, but no equivalent procedure would be used to ensure they are not double-counted. Environmental advocacy groups like Greenpeace and the World Resources Institute said the proposal was insufficient because it could allow credits to get double-counted in private markets. China and other countries oppose Japan"s proposal, according to two delegates, who were not authorized to speak to the media. Jennifer Morgan, head of Greenpeace International, told Reuters the proposals were "very, very worrying". Negotiators are still struggling to strike a deal on whether offset credits from a past UN system will be carried forward and traded in the new carbon market. One compromise under discussion would only carry over credits produced after either 2013 or 2016, to attempt to soothe some countries" concerns that older credits would flood the new market with cheap offsets that countries could buy up instead of actually reducing emissions. The latest deal draft also included rules that would effectively stop countries counting those older credits towards their climate targets after 2030. Meanwhile, poorer countries are still pushing for a tax on carbon offset trades between two countries, with the proceeds going to a fund to help developing nations adapt to climate change. Those countries are furious rich countries have failed to meet their past promises to deliver climate finance, and say taxing carbon market trades would ensure funds. "We are a little bit disappointed - actually a lot disappointed - that we are still haggling about the share of proceeds," Kenyan environment cabinet secretary Keriako Tobiko said on Friday. Rich countries including the United States, Canada and 27-country European Union have opposed the tax. "I"m not sure this is an issue where we will be able to make a lot of progress here in Glasgow," Canadian climate minister Steven Guilbeault told Reuters. Outside of the carbon market talks, negotiators at COP26 are locking horns on a range of other issues, including how often countries will be required to set new climate targets and whether rich nations should offer financial compensation for the losses and damages climate change has already caused in poor countries. Delegates said they expected to negotiate late into the night and potentially through the weekend.