BRUSSELS (Reuters) - Changes to future EU gas storage targets being negotiated by European Union countries could, if approved quickly enough, also soften this year's binding storage-filling requirements, EU diplomats told Reuters.

EU countries are negotiating changes to future gas storage filling obligations for 2026 and 2027, including swapping their current binding target to fill storage 90% by November 1 for an aim to hit the same filling level any time between October 1 and December 1.

But these changes could also apply to this year's November 1 target, if the rules are finalised and published ahead of that date, the EU diplomats said.

The gas storage rules were introduced in 2022 after Russia slashed deliveries following its invasion of Ukraine, to ensure EU countries had a buffer of stored fuel during winter.

A negotiating document, published on Wednesday by Poland - which holds the EU's rotating presidency and chairs negotiations among its member countries - confirmed the planned changes to the gas storage rules would apply from the day after they are published in the EU's official journal of laws.

EU countries aim to agree their joint position on the rules next week, after which they must negotiate the final law with the European Parliament.

It could take months before the rules are agreed and published as an EU law - likely meaning it would affect the November filling target but not the other goals countries face in the months before, one of the EU diplomats said.

The EU also has gas storage filling targets for February, May, July and September. The countries' proposal would make these targets voluntary in future years.

With negotiations ongoing, the implications for the 2025 targets - as well as the other amendments countries have proposed to future targets - could still change.

The European Commission had initially wanted to extend the current system of binding targets that must be met by certain dates for two more years.

But that idea met resistance from governments including Germany, France and the Netherlands. Countries want looser rules because of concerns the targets inflate gas prices by indicating to the market that European buyers must buy large volumes of fuel by fixed deadlines, creating an opportunity to manipulate prices.

The latest negotiating document showed that as well as tweaking the EU's November storage-filling target, member states would be allowed to deviate by up to 5 percentage points from the requirement to fill gas storage by 90%, in case of "unfavourable" market conditions.