Iranian President Mahmoud Ahmadinejad is in Azerbaijan for a two-day visit, the latest in a flurry of diplomatic contacts with neighbouring US allies.
Azerbaijan says it will not let the US use its territory to attack neighbours
Iran and Azerbaijan are both oil-rich, predominantly Shia countries with close cultural and economic ties.
Iran appears keen to show it can play a positive role in the region, despite US suspicions about its intentions.
Iranian officials have met Iraq's prime minister and Mr Ahmadinejad has visited Afghanistan for the first time.
Both the Iraqi and Afghan leaders praised what they said was the positive role Iran is playing in helping their countries, despite allegations from Washington that it is trying to stir up trouble in both nations.
Iran and Azerbaijan have long-running differences over the legal status of the Caspian Sea - Tehran suspects elements in Azerbaijan of trying to whip up nationalist Azeri sentiment within Iran's large Azeri ethnic minority.
Last year, ethnic Azeris in both countries were outraged by an Iranian newspaper cartoon implying cockroaches speak Azeri.
But given Baku's close ties with Washington, Iran may also be seeking further assurances that Azerbaijan will not allow the US to use its territory against Iran.
Azerbaijan has repeatedly said it would not allow American troops to use its territory to attack neighbouring countries.
Iran may also want to discuss a Russian proposal that Washington and Moscow could use a radar station in Azerbaijan for a joint missile-defence project.