LONDON (REUTERS) - Dominant Mercedes plan to block an attempt by Formula One rivals to relax the rules and allow engine development during the course of next season.

The engine rules are currently "frozen" in-season to keep costs down after the introduction of costly new V6 turbo hybrid power units this year.

Renault-powered rivals Red Bull, dethroned by Mercedes as constructors' champions last weekend, and Ferrari want the rules relaxed to allow in-season development that might give them a chance to close the gap.

Mercedes motorsport head Toto Wolff said in Russia last weekend that his team had already voted against the proposal in a strategy group meeting and would do so again when the matter goes to a Formula One commission meeting.