CME Group, operator of the largest US futures exchange, has launched a pre-emptive strike against rival exchange operator NYSE Euronext by slashing the cost of trading its two flagship futures products in a bid to undermine similar plans by its New York rival.

The move comes less than two weeks after NYSE Euronext and Deutsche Börse unveiled plans to combine, creating what would be the world's largest exchange.

NYSE Euronext's futures arm, NYSE Liffe, is only weeks away from launching a challenge to the CME's near monopoly of trading in interest rate futures, known as eurodollars and one of the most widely traded derivatives contracts in the world.

It has teamed up with the Depository Trust & Clearing Corporation, the New York-based post-trade services group, to offer "cross-margining" - where trading positions across products on the exchange are taken into account when assessing how much margin, or upfront cash, is needed to guarantee against default.

These margin payments are one of the main costs associated with trading derivatives on exchanges. Currently, traders have to pay margins on each specific product.

However, on Monday the CME said it would offer similar cross-margining between eurodollars and US Treasury bond futures, in a clear attempt to undermine NYSE Liffe's effort before it was launched.