ATHENS, Greece (AP) — Financially-struggling Greece has signed contracts for offshore gas exploration in large tracts of the Mediterranean, despite warnings from leading environmental groups that the project threatens key marine life habitats.

The deal will allow global energy giants Total and ExxonMobil, together with Greece's Hellenic Petroleum, to explore two areas covering 40,000 square kilometers (15,000 sq. miles) south and southwest of the island of Crete.

Greenpeace and the World Wide Fund for Nature have appealed to Greece's supreme court to block the project. They say prospecting in deep waters off Crete will threaten endangered whales, dolphins and other marine life, and argue that Greece would do better to invest in renewable energy sources.

Left-wing Prime Minister Alexis Tsipras hailed Thursday's signing as a boon to Greece's economy and promised strict environmental safeguards.