Gunboats from Azerbaijan's coast guard threatened international oil company ships working on behalf of Turkmenistan on at least two occasions in 2008, U.S. diplomatic cables from Wikileaks show. The incidents, which don't seem to have been previously reported, caused Turkmenistan's president, Gurbanguly Berdimukhammedov, to accuse his Azerbaijani counterpart Ilham Aliyev of "personally insulting" him and "running like a little boy." One incident was in April 2008, and involved a vessel from the Malaysian company Petronas in a part of the Caspian that both sides agree is Turkmenistan's:

[U]pon closing in on the Petronas ships/rig, the Azeri gunboats instructed the Petronas captain to move away. He reportedly refused to move, stating that he was nowhere close to Azerbaijan's claimed border. The standoff reportedly lasted for more than a day. In the end, the Petronas captain agreed to move slightly to the east (although not as far as the Azeri border guards at first had demanded), which apparently satisfied the Azeris.

The second was in May 2008 and involved a ship from Canadian company Buried Hill and was in a spot that was (and remains) in dispute between the two countries, around the Serdar/Kyapaz and Omar-Osman/Azeri-Chirag-Guneshli fields:

In the second episode, the Azeri gunboats again intercepted a vessel that Buried Hill had hired to do some research in block III related to its plans to begin drilling in the first quarter of 2009. Buried Hill told him this time calls were made from Ashgabat to Baku, and that the Azeri vessels subsequently backed off. According to Buried Hill, there were also Iranian vessels in the area at the time of the interception.

According to one of the cables, the scuttlebutt among oil companies was that BP, working on the Azeri side, was drilling diagonally into Turkmenistan's zone (to borrow a phrase from There Will Be Blood, drinking Turkmenistan's milkshake):

[T]here are rumors and strong speculation circulating among foreign oil firms that BP, the company drilling in ACG, may have drilled a diagonal spur off its main bore hole toward the Serdar/Kyapaz field. This, he suggested, would explain why the Iranian vessels were in the area -- and why the Azeri coast guard appears to be so jumpy about any vessels that are not clearly in transit.

In a later cable, Berdimukhammedov fumes to the U.S. charge d'affaires that Aliyev was engaged in "hooliganism". The cable quotes Berdimukhammedov at length:

Even with the recent 'Azeri stupid mistakes,' we are committed to moving forward, but the Azeris haven't made it easy because their patrol boats attacked our vessel (in Serdar/Kyapaz) just days before my visit to Baku. We'd been there for three months, and they knew it! Why did they wait until my visit? That was a personal insult! I've been the one who's taken all the steps -- at your urging. I approached Aliyev in Saint Petersburg (at the CIS informal summit in 2007). I made the first phone call to him. I agreed to visit Baku before he visited Ashgabat -- on your advice! I stood up to Putin for our sovereign rights at the 2007 Caspian Summit in Tehran, but Aliyev ran like a little boy. And what did I get for all of this? A slap in the face!"

And he said be brought up the issue with Aliyev, who claimed ignorance:

Berdimuhamedov explained that when he had been in Baku, he had a polite but tough private one-on-one meeting with Aliyev, and had asked why Aliyev had sent patrol boats into Serdar/Kyapaz to challenge Turkmenistan's claim to the disputed block. Berdimuhamedov said Aliyev responded that we was out of the country at that time and had been unaware of the event. Berdimuhamedov said, "I didn't say anything then, but he IS the president, and he needs to know what is happening in his name in his own country, if he is really in charge."

Ouch. Remarkably, though, U.S. diplomats didn't think that the incident would necessarily scuttle plans to build a pipeline across the Caspian from Turkmenistan to Azerbaijan, though they said personal pique could get in the way of strategic interest:

We continue to wonder if Turkmenistan and Azerbaijan are further along on Caspian cooperation than either side is letting on as they attempt to keep it under the Russian radar. However, if Berdimuhamedov's wounded fulminations against Azerbaijan and President Aliyev were an act, he should be nominated for an Academy Award. What we probably need to recognize is that Berdimuhamedov, for all his pretences at statesmanship, is still seriously hobbled by the traditional Turkmen inferiority complex about Azerbaijan, which harks back to the early 20th century when the Soviets tried to use the more urbane Azeris to "civilize" the Turkmen nomadic tribes. It will not be easy, given the presidential bulls-pawing-the-turf in this region, but we need probably to try to explain to Azerbaijan the need for unaccustomed, high-road sensitivity in dealing with the brittle Turkmen. Our arguments should always be strategic, and never appear to favor one protagonist over another. From all the hints he dropped, we believe Berdimuhamedov has not given up on the concept of a Turkmen-Azeri natural-gas inter-connector pipeline. But, at the moment, he appears -- unless it's a huge act, and even if he exaggerated for effect -- to be bruised and frustrated. He needs realistic reassurance at the highest level. It's in our national interest for energy security to do so.

And plans for such a trans-Caspian pipeline aren't dead yet, so Berdimukhammedov must have gotten over his hard feelings.