An invitation for bids for data control mechanisms on the planned Trans-Adriatic gas pipeline puts it one step closer to completion, developers said.

The pipeline consortium developing the planned natural gas pipeline said it was inviting companies to pre-qualify for the supply and delivery of a centralized monitoring system as well as a fiber optic cable network meant to feed back to a supervisory control center.

"With the launch of these final pre-qualification notices, TAP reaches another important milestone in its procurement process," TAP Project Director Norman Ingram said in a statement.

TAP is slated to transport natural gas from the second phase of the Shah Deniz natural gas field off the coast of Azerbaijan as early as 2019.

BP, leading Azeri developments alongside a state-backed energy company, has awarded more than $1 billion in development contracts since selecting the TAP as its option for Shah Deniz in 2013. TAP would connect to the Trans-Anatolian natural gas project running through Turkey to the Greek border.

Lingering economic and geopolitical issues in Ukraine pose a threat to European natural gas supplies. Europe gets about a quarter of its gas needs met by Russia's Gazprom, accused of holding monopolies in the region, and the majority of that volume runs through Soviet-era pipelines in Ukraine.

TAP is part of a string of networks meant to diversify the European energy sector.

Pipeline construction is slated to begin in 2016.