(Add no comment from Equitix and Kepco in paragraph 6)

By Andres Gonzalez

LONDON, Nov 17 (Reuters) - Spanish utility Iberdrola is planning to make an offer for Electricity North West (ENWL) that could value the British power distribution network at up to 3.5 billion pounds ($4.34 billion), two sources familiar with the matter said.

Sources told Reuters in October that ENWL's shareholders are working with investment bank Jefferies on a strategic review of the network operator, which delivers electricity to some five million customers in Manchester, Lancashire and Cumbria.

Iberdrola declined to comment on any involvement in the ENWL sale process, which one of the people, who spoke on condition of anonymity, said is expected to start in December.

ENWL is owned by a consortium led by Japan's Kansai Electric Power Co. (Kepco) and investment fund Equitix, which both own 40% stakes, the company's annual report shows.

Macquarie and KKR may also consider bids for ENWL, one of the people and a third person with knowledge of the sale process said, adding that deliberations are at an early stages and there is no certainty they will result in a deal.

Macquarie, KKR, Equitix and Kansai Electric spokespeople declined to comment.

Buying ENWL could help Iberdrola connect areas that it already serves through its Scottish Power business. This provides power to 3.6 million customers in Merseyside, Cheshire, North Wales and North Shropshire in England and Central and Southern Scotland, its latest annual report shows.

The Spanish group considered an offer for ENWL in 2019, when its then owners JP Morgan and Colonial First State launched a sale that was finally won by the current shareholders.

Iberdrola is ramping up its investments in electricity networks, aiming to deploy 27 billion euros until 2025, with the goal of achieving 30% growth in core earnings of its networks unit to up to 8.5 billion euros.

This figure is equivalent to 57% of the total investments planed by Iberdrola between 2023 and 2025, which will be partially funded by asset sales.

Iberdrola expects to receive around 6 billion euros from partnerships and asset sales by the end of the year that will help it close 2023 with a net debt of around 43 billion euros, roughly in line with 2022.

($1 = 0.8067 pounds) (Reporting by Andres Gonzalez; additional reporting by Pietro Lombardi; editing by Anousha Sakoui and Alexander Smith)