The presidents of Russia, Iran, and Azerbaijan met in Baku this week, for the first time in this trilateral format, part of a week of heavy diplomatic activity that highlighted the shifting international relations around the South Caucasus.

The Baku meeting took place on Monday, and was taken on the initiative of Azerbaijan. The top agenda item was a railroad project that could connect Russia and Eastern Europe to the Persian Gulf.

That project would bring not only economic benefits to the three countries, but could be a geostrategic boon for Azerbaijan, as well, said Zaur Shiriyev, a Baku-based political analyst. He noted that this project would compete with another Russia-initiated North-South railroad project, that would go from Russia through Abkhazia, Georgia, and Armenia.

"This transport corridor bypasses Armenia, thereby eliminating the possibility of reopening the Russian-Georgian railway though Abkhazia, or any kind of discussion that was used a threat [against] Baku," Shiriyev said in an email interview with The Bug Pit. He noted that that Armenia project also could have competed with another Azerbaijani rail priority, the currently under-construction Baku-Tbilisi-Kars railway that will connect Azerbaijan to Turkey and Europe.

But Azerbaijan's partners may have other ideas. "Finally we will be able to connect the Caucasus countries, Russia, northern and eastern Europe to the Persian Gulf," Iranian President Hasan Rouhani said at the meeting. The news site Commonspace.eu noted that Rouhani "further expressed hope that the corridor would contribute to boosting economic ties of all regional countries, a thinly veiled reference to the fact that Iran wants to see Armenia as part of this project."

For its part Russia used the meeting to push the idea of Iran joining its Eurasian Economic Union. "President Putin's aim is for Iran to join a Eurasian Economic Union (EEU), initiated by Russia, beginning with Iran joining an EEU Free Trade zone," the Tehran Times reported. Russia would no doubt love for Azerbaijan to join, too, but no mention of that was made in Baku. Armenia already is a member of the EEU, which in itself would seem to eliminate the possibility of Azerbaijan joining, but even that aside, Baku is loath to give Russia that much control over its economy.

The three sides also discussed the dispute over the status of the Caspian Sea, which has lately appeared closer to resolution, though it's still not clear how Iran -- which holds a stubborn, and contrary, position to that of its other neighbors on the sea -- is willing to compromise. "To overcome some of the problems related to the Caspian Sea, some quick work has to be done," Rouhani said after the meeting.

Russia and Azerbaijan also discussed some military cooperation issues; Russian Deputy Prime Minister Dmitry Rogozin came along and announced that Russia intended to build an aircraft assembly plant and a helicopter modernization plant in Baku.

The meeting in Baku was just the start of a busy schedule of regional diplomacy for Russian Vladimir Putin. The day after the Baku meeting he met with his Turkish counterpart Recep Tayyip Erdogan in St. Petersburg to formally patch up the relations which were abruptly soured last year when Turkey shot down a Russian military jet on the Turkey-Syria border. And on Wednesday, Putin met with Armenian President Serzh Sargsyan to discuss resolving the conflict over the territory of Nagorno Karabakh.