TBILISI -- A deal breaking the deadlock between Georgia and oil major BP on the route of the planned Baku-Tbilisi-Ceyhan (BTC) oil pipeline had still not been signed late Sunday as marathon talks entered a fourth day, a Georgian official said.

The two sides are tantalizingly close to agreement on ecological safeguards for the $2.95 billion pipeline project, which will export crude oil from the Caspian Sea through Georgia and Turkey to world markets.

But the deal had still not been signed late Sunday, Maya Kapanadze, spokeswoman for Georgia's Ecology Ministry, told AFP.

The crisis talks, which have been going on in the Georgian capital Tbilisi since Friday, were called to resolve Georgian concerns that the pipeline's route was too close to the ecologically-sensitive Borjomi valley.

Georgia had refused to sign a report on the pipeline's environmental impact until those concerns were allayed, but project operator BP warned construction would be thrown off schedule unless the Georgians signed.

Azerbaijan and Turkey have already approved environmental impact assessments for their countries, leaving Georgia as the odd man out.

BP had set a deadline of midnight on Saturday for Georgia's government to sign the document. A spokeswoman for BP said Sunday that a deal had been reached in principle and the documents would be signed later the same day.

But both predictions proved optimistic as Georgian negotiators held out for extra environmental safeguards.

If Georgia fails to approve the pipeline, the delays would cost the BTC consortium millions of dollars and would be likely also to attract the anger of the United States' government, a strong backer of the project.

When it comes on stream in 2005, the BTC pipeline will export up to one million barrels of oil a day from Azerbaijan, on the Caspian Sea to Turkey's Mediterranean Coast port of Ceyhan.

Georgia, backed by Western environmental groups, has said it is worried about the impact on the Borjomi valley, a national park which is also the site of world-famous mineral water springs.

BP has countered that its engineers have gone out of their way to protect the area's ecology by installing extra safeguards, and pointed out that the pipeline will pass 15 kilometers (10 miles) from the Borjomi valley.

The consortium financing the pipeline is made up of BP, Azerbaijan's state oil company Socar, Unocal, Statoil, Tpao, Eni Agip, TotalFinaElf, Itochu, Inpex, Delta Hess and Conocophillips.