Bosphorus tunnel venture seeks investors -sources

* Equity wanted to help finance project - sources

* Infrastructure funds targeted - source

* Commitments sought of at least $50 million - source By Greg Roumeliotis and Thomas Grove

AMSTERDAM/ISTANBUL, Oct 1 (Reuters) - A Turkish-Korean consortium awarded a 30-year concession to build and operate a $1 billion tunnel across the Bosphorus is looking for equity co-investors, two people familiar with the situation said.

A joint venture between Turkey's unlisted Yapi Merkezi and South Korean firms Samwhan Corporation, SK, Kukdong, Namkwang 001260.KS and Hanshin hopes the equity raised will help finance what is a technically challenging project, the sources said.

“They have approached investors, infrastructure funds in particular, about making equity commitments of at least $50 million,” one source said.

The existing members of the consortium will dilute their stake in the project company on a pro rata basis based on the equity commitments made, the source said.

Yapi Merkezi and Samwhan, the lead companies in the consortium, did not respond to a request for comment.

The project will connect the continents of Europe and Asia through a 14.5 kilometre tunnel, of which 5.4 km will be a submarine tube below the Bosphorus Strait.

The construction risks of the scheme have made it difficult to attract project financing. The construction of the Marmaray rail tunnel, which will the first tunnel to cross the Bosphorus, has been delayed for years due to archaeological findings and has yet to be completed.

Unlike Marmaray, which is a rail tunnel, the Bosphorus tunnel will be used for light vehicle traffic, with the government guaranteeing a minimum revenue from tolls for the operator.

The consortium hopes it can sign its contract this year provided negotiations with the government can be completed, the same source said.

Unicredit, which is advising the project company on the financing, also has the mandate to find co-investors in the consortium, the source said. (Editing by Rupert Winchester)