As Alvaro González, captain of the Bosco Tapias, waited three weeks for a 30-vessel traffic jam to clear so he could begin the treacherous journey through the Bosporus and Dardanelles straits, he used the time to get his 274-meter oil tanker shipshape.

"Maintenance, cleaning and painting are the usual activities when the tanker is anchored waiting," he said. But for the oil companies that have hired the tanker, there is nothing usual about the task, or its price tag: $50,000 (€40,000) a day.

Refiners in the Mediterranean are suffering one of the worst and most costly shortages of oil since the Gulf war in 1991.

The reason for the delays, of up to 25 days since the start of the gridlock in the Turkish straits in December, is a mix of environmental, security and geopolitical factors which few industries other than oil face to such a degree.

"Shipping across the Bosporus straits is like sailing in a canyon, you see land from portside to starboard. It's really narrow and highly risky," says Captain Miguel Mendoza, chief of operations of the Naviera Tapias, the company that owns the Bosco Tapias.

"The most crowded area is Istanbul. Oil tankers have to contend with the city's tourist ferries, small fishing boats, cargo ships, commuter ferries darting from one side to the other. For the people in Istanbul, crossing at the same time as an oil tanker may be usual. For us, it is highly unusual."

Collisions and groundings are the most frequent accidents for a waterway that at its narrowest point could not fit a tanker lengthwise.

The doubling of oil exports from Russia in eight years, and the rush of oil expected from the Caspian have worried Turkish authorities and international oil companies, whose reputations ride on their safety record.

Together with BP, Ankara has pushed for the construction of the Baku-Tblisi-Ceyhan pipeline, a $3bn project that is about to get the backing of 15 commercial banks, after securing the support of development banks in the US and Europe in October.

European oil executives blame the jam in the Bosporus in part on new Turkish regulations.

They say the rules have at least as much to do with the country's campaign to speed the pipeline's construction and maintain Turkey's unique geopolitical importance as one of the region's most important oil export points as they do with environmental safety and terrorism concerns.

"Turkey wants more pipelines to reinforce its geostrategic position and, at the same time, gain access to fees from the oil transit in the pipelines, essential for the economic recovery of the country," said one foreign oil executive who dealt with Turkey's energy policies.

The Turks have been willing to use the Bosporus as a lever before.

Tansu Çiller, former Turkish prime minister, in 1995 threatened western governments that "not a drop of oil would pass through the Bosporus" if Turkey lost the pipeline.

This battle over control of the Caspian's oil and natural gas riches has raged since the early 1990s, with the US backing a system of pipelines that would bypass Iran as well as reduce Moscow's grip over countries such as Azerbaijan, Tajikistan and Kazakhstan.

One of the starkest examples of Russia's resolve and Turkey's ability to play both sides is the struggle over Tajikistan's natural gas exports.

After almost a decade, Tajikistan lost its campaign to sever its dependency on Russia by building the Trans Caspian pipeline to Baku with the help of Royal Dutch/Shell, General Electric and the support of the US government. The fight cost the country an 85 per cent plunge in its natural gas production.

Tajikistan finally relented in 2000 and agreed a 15 year contract with Russia after its Trans Caspian pipeline was rendered uneconomic when Russia, Turkey and Italy agreed a competing Russian pipeline beneath the Black Sea, an industry executive explained.

Refiners and tanker captains waiting for the 30-ship backlog in the Bosporus and Dardanelles straits to clear sympathise with Turkey's security concerns, but like Tajikistan before them they believe they are also the victims of geopolitical manoeuvring.