LONDON (Reuters) - Hopes French Guiana has commercial oil reserves like those of Ghana across the Atlantic suffered a new blow on Tuesday as a well off the Latin American country's coast came in dry for explorers Tullow Oil (>> Tullow Oil plc) and Royal Dutch/Shell .

Tullow's production in Ghana has helped finance exploration across Africa and tempted it off the coasts of French Guiana, Suriname and Guyana - to which west Africa was connected millions of years ago, and which has similar geology.

Tullow's stock slid 7.7 percent to 1,029 pence on the news.

The dry hole in the GM-ES-4 well is a much smaller setback for operator Shell, the world's second largest investor-owned oil company, and for another big partner Total (>> TOTAL).

But it follows disappointing drilling results in two other French Guiana wells. The partners will now drill a final well in the area where they made the Zaedyus 1 oil discovery in 2011 before deciding on their future there.

"French Guiana commerciality remains uncertain," said Morgan Stanley analysts in a research note.

"Whilst it is highly unlikely there is only one Zaedyus-scale discovery in French Guiana, we now expect Tullow to spend time analyzing its current position before progressing further."

Tullow also said a well off the coast of Mozambique in the Rovuma basin had discovered uncommercial amounts of gas, but that there was encouraging evidence of the oil it is also looking for.

Tullow is partnered with another big international oil company, Norway's Statoil (>> Statoil ASA), off the coast of Mozambique - a hotspot for gas development.

"The potential for discovering oil in this region remains after we encountered wet gas shows in the deeper sidetrack. We will integrate this valuable data into our regional model to improve our chances of unlocking the oil play potential offshore Mozambique," Tullow Exploration Director Angus McCoss said.

In Mozambique, an exploration hot spot after huge gas discoveries made in recent years, Tullow said that the first deep water well drilled in area 2 found gas but not in standalone commercial quantities.

This year, Tullow has been under pressure to deliver positive drilling news. Oil finds in Kenya helped deliver a boost to its prospects earlier in July.

Two small British explorers, Wessex Exploration (>> Wessex Exploration plc) and Northern Petroleum (>> Northern Petroleum Plc) also own 1.25 percent stakes in the licence in French Guiana. Their shares retreated 28 percent and 6 percent respectively.

(Additional reporting by Andrew Callus; editing by Kate Holton)

By Sarah Young