Clearing houses, vital parts of the electronic plumbing which helps markets run, stand between two sides of a trade to guarantee its completion even if one side goes bust.

Without EU agreement that Swiss financial rules are equally strict as the 28-nation bloc's own standards, customers using the London Stock Exchange and other platforms across Europe could face higher costs, because if they chose to continue using SIX without it getting equivalence, they would have to hold more capital.

"So far as we can judge, the process is on track and we hope to get equivalence this year," Tomas Kindler, head of clearing at SIX Securities Services, part of the Swiss trading-to-clearing and settlement group.

Reuters reported this week that similar negotiations between the EU and the United States had not proceeded well enough to meet a June deadline, forcing the European Commission to seek EU member state backing for extending the deadline to December, its third six-month delay.

Kindler said obtaining equivalence for SIX would be a big milestone, reducing pressure to decide on whether it should open a clearing house physically inside the EU.

The United States, which along with the EU accounts for most of the world's $700 trillion (£462.66 trillion) derivatives market, uses different rules, raising the prospect of European clearing houses having to abide by two sets of standards.

EU financial services chief Jonathan Hill told reporters on the sidelines of an EU finance ministers' meeting in Riga he was unable to say when there would be a deal with U.S. regulator the Commodity Futures Trading Commission (CFTC).

"I hope that we can make some progress on that in the near future, but precisely the timing of when that pans out and what happens when, I cannot yet say, because it takes two to tango," Hill said. "So we sent some suggestions to the CFTC and we need to see how to move that forward."

An EU source said there was a need ensure European clearing houses have access to U.S. markets.

"Neither side has finally agreed yet on this but we are in a much more advanced place in terms of mutual recognition. That is not really an issue now," the source said.

There were a range of ways to deal with remaining key technical differences in applying margins to derivatives trades to cover defaults or swings in prices.

"Both sides are cognisant of the fact that finding a way to reconcile our standards would be the most effective way to move forward," the EU source added.

(Editing by Mark Potter and David Holmes)

By Jan Strupczewski and Huw Jones