Gazprom and Socar signed a deal Monday giving the Russian company first rights to Azeri gas previously seen as reserved for the Nabucco pipeline, capping President Dmitry Medvedev's "short but intensive" visit to Baku.

Medvedev said the agreement was based "absolutely not on political motives but on mutual benefits," although analysts said Gazprom was essentially staking out a claim for Azeri supplies to fill its South Stream pipeline project, the main rival to the European Union-backed Nabucco.

Under the deal -- signed by Gazprom chief Alexei Miller and Rovnag Abdullayev, head of the State Oil Company of Azerbaijan -- Gazprom will buy a relatively modest 500 million cubic meters of gas from Socar next year.

Speaking to reporters after the signing, Miller declined to comment on the base price outlined in the agreement. Purchases will be made using a pricing formula, while the "basic price outlined in the agreement is commercially attractive for our Azeri partners," he said.

Miller also said it would be possible to increase the volume later.

To be attractive for Azerbaijan, the sales would probably be tied to the market price in Europe and amount to "at least $180" per thousand cubic meters, said Vitaly Gromadin, an analyst at Arbat Capital.

Azerbaijan also recognized Gazprom as a priority buyer from Stage 2 of the Shah Deniz gas field.

"All things being equal among potential buyers, priority will be given to Gazprom," Miller said. "Other buyers would have to offer conditions that are more financially attractive," he said.

Medvedev also hinted that Monday's deal was just the beginning of Gazprom's plans for Azeri gas. "I think we can further continue this work, keeping in mind the big opportunities and big volumes, which will be growing," he said after the signing.

The agreement is the first gas import deal between Russia and Azerbaijan, which had been the only CIS country without a contract to sell the fuel to Russia. Miller said Friday that the gas would be used in southern Russia.

Azeri President Ilham Aliyev said his country would increase its gas output by 11 percent next year to 30 billion cubic meters.

Stage 2 of Shah Deniz was supposed to be a key source for the Nabucco pipeline, which European countries have pushed to diversify their energy imports and lessen reliance on Russia.

Gazprom has not looked favorably on these efforts. On Friday, Miller warned Europe not to turn diversification "into a fetish," and he called alternative suppliers too inexperienced.

For now, Gazprom does not need the Azeri gas because of lower demand, but the dea's priority clause may play an important role in the future as Russia lobbies for South Stream, Gromadin said.

"An agreement with Azerbaijan will show a stronger Gazprom position to potential Nabucco investors," he said, and it also gives the company extra security as Turkmenistan becomes a less reliable exporter.

Gazprom has expressed interest in developing and buying all the gas from Stage 2 of Shah Deniz, which can produce 16 bcm of gas annually. "It's a question of who builds the pipeline faster," Gromadin said.