Telco reportedly wants more control over its infrastructure in major cities.

Vodafone UK and O2 are renegotiating their network-sharing deal, it emerged over the weekend, as Vodafone seeks greater control over its mobile infrastructure.

According to a Sunday Telegraph report, the agreement has become a source of tension between the two telcos. Vodafone in particular wants more autonomy in major cities so it can add capacity and improve coverage more quickly. In the report, O2 is also alleged to be sluggish when it comes to maintaining infrastructure.

Taking greater control of its networks would help Vodafone respond more effectively to BT-owned EE, which has been working hard to extend LTE coverage to more locations and add extra capacity in high-traffic areas.

Vodafone and O2 established their network-sharing joint venture in 2012. Called Cornerstone, Vodafone was given responsibility for rolling out infrastructure in the west of England, Wales, and south London, while O2 was made responsible for the east of England, Northern Ireland, Scotland, and north London.

Sources cited in the Telegraph report claim that Vodafone wants "certain changes in the joint venture so it can invest its own money and run its own show where it thinks it makes a difference."

In return, O2 would gain more long-term certainty for Cornerstone, which could prove significant as O2 parent Telefonica works towards an IPO of its U.K. business.