The EU proposed a package of emergency measures to tackle soaring energy prices earlier this month, but has steered clear of a gas price cap, an idea which has split the bloc's 27 member states.
Countries in favour stepped up pressure on Brussels, with a letter asking the European Commission to make proposals on a gas price cap for discussion at a meeting of EU energy ministers on Friday, followed by a legislative proposal as soon as possible.
"We acknowledge the efforts made by the Commission and the measures it has put forward to face the crisis. But we have yet to tackle the most serious problem of all: the wholesale price of natural gas," said the letter addressed to Energy Commissioner Kadri Simson and seen by Reuters.
The document was signed by ministers from 15 countries: Belgium, Bulgaria, Croatia, France, Greece, Italy, Latvia, Lithuania, Malta, Poland, Portugal, Romania, Slovakia, Slovenia and Spain.
The letter that Reuters had seen a draft of earlier called for a price cap on all wholesale gas transactions.
It said capping gas prices would help countries rein in "untenable inflationary pressures" hitting households and businesses, and could be designed in a way that ensures security of supply.
Other states oppose capping gas prices, raising doubts as to whether any EU proposal would win sufficient support.
Germany, the Netherlands and Denmark say capping prices could endanger the security of supply by undermining the EU's ability to attract gas deliveries this winter.
Russia has slashed gas deliveries to Europe since the West imposed sanctions on Moscow after Russia invaded Ukraine, leaving countries scrambling to secure alternative supplies.
So far, the European Commission has proposed emergency EU measures including windfall profit levies on energy firms, and cuts in electricity use.
EU countries are negotiating those proposals and aim to approve them when EU energy ministers meet on Friday.
(Reporting by Gabriela Baczynska; writing by Sabine Siebold; editing by Jonathan Oatis)
