LONDON, Jan 29 (Reuters) - Britain's Competition and

Markets Authority said on Wednesday it was weighing whether a

merger of Spain's Iberdrola and NWEN Ltd could reduce

competition in the energy sector, and make it tougher for market

regulators to keep track of pricing.

The CMA has set a deadline of February 12 for submissions by

interested parties to phase 1 of its merger enquiry, and a

deadline of 27 March for the phase 1 decision.