MILAN/LONDON (Reuters) -Spanish gas grid operator Enagas is in talks to acquire Singaporean sovereign wealth fund GIC's 32% stake in Terega, France's second-largest gas transmission operator, according to two people familiar with the situation.

Terega is also a partner of the Spanish company in a hydrogen pipeline project to connect Spain and France and the companies also operate gas pipeline connections between the two countries.

The stake could be worth around 600 million euros ($693.60 million), with the French company's valuation, including debt, estimated at around 4 billion euros, according to one of the people. Enagas market capitalisation was 3.6 billion euros as of Monday's close, according to LSEG data.

No deal is certain, the sources said, speaking on condition of anonymity as the conversations are private.

Enagas and GIC declined to comment. Terega declined to comment on the talks and did not respond to a request for comment on the valuation of the stake.

A deal with GIC could help Enagas meet its stated target to accelerate investments in hydrogen infrastructure.

Terega and Enagas, alongside Engie unit Natran, are members of a joint venture to develop a cross-border hydrogen pipeline between the Spanish city of Barcelona and the French port of Marseille.

It is a part of a larger 2.5 billion euro H2Med hydrogen pipeline project that will link Portugal, Spain, France and Germany by 2030. 

The European Union is hoping to replace some natural gas use with hydrogen, which does not emit CO2 when burned.

Terega's shareholders include Italian gas grid operator Snam with a 40.5% stake, French state-owned utility EDF, which has 18%, and French bank Credit Agricole with a 10% stake, according to the French company's website.

Last year, Reuters reported that EDF and Credit Agricole were exploring selling their stakes in Terega although a deal has not materialized.  

($1 = 0.8651 euros)