A. The Caspian Sea, with its vast mineral resources, has been a problem since the collapse of the Soviet Union. It's estimated that there are 70 billion to 200 billion barrels of oil beneath the waters, which makes it an extremely desirable place to the five states with Caspian coastlines - Iran, Azerbaijan, Russia, Kazakhstan and Turkmenistan. They are currently are in dispute on how to divide up the sea.
Western oil companies have invested heavily in Azerbaijan and Kazakhstan, so the West has a major interest in this dispute, too.
Q. What's the problem
A. Azerbaijan and Kazakhstan want it treated as a sea, which would entitle them to their own territorial zones.
Russia and Iran, however, claim that treaties from the Soviet era define it as a lake, and international law regarding lakes would mean that these countries would get a bigger piece of it. Their claim is backed by Turkmenistan, which has an extremely erratic leadership.
Q. So what's happened
A. At the end of July, an Iranian ship forced two BP oil-exploration ships (run jointly by the UK and Azerbaijan) away from a disputed part of the Caspian Sea. Then Iran sent military aircraft into air space claimed by Azerbaijan, claiming that, as the borders were not determined, it was doing nothing wrong. Then the Iranian ambassador left Azerbaijan's capital (although he's said to be returning).
There there was a report in the� Tehran Times on July 26 which said, 'Following the imprudent act of Azerbaijan, supported by Britain, Iran has deployed its military ground forces to the Iran-Azerbaijan borders. This report was subsequently denied.
Q. What was the response to these moves by Iran
A. BP immediately suspended drilling in the disputed oilfield.
The US has shown its support for Azerbaijan, saying that Iran had been 'provocative'.
Russia is urging calm, despite the fact that it has been flaunting its military strength in the Caspian. In January, it conducted exercises with live ammunition, and last month, Russian officials announced that three new ships were joining the Caspian fleet.
Q. So what happens next
A. Much holding of breath until the autumn, when the presidents of all the Caspian countries are due to meet. Meanwhile, watch this space...
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By Sheena Miller