General Charles "Chuck" Wald, Deputy Commander of the US European Command, visited military installations and had talks with Azerbaijan's President Ilham Aliyev.
The Azeri state news agency quoted the general as saying that Washington was offering unspecified military aid which "is important from the point of view of regional security, including in the Caspian. The Pentagon attaches great importance to this."
The Caspian Sea is thought to hold the world's third-largest oil reserves. Washington is keen to exploit the oil as an alternative to the Middle East, and is backing energy projects in the region.
However, there are unresolved security problems associated with the inland sea. Iran is staking claims to oil fields which Azerbaijan insists lie inside its sector of the sea.
The Pentagon has already committed to provide four million dollars of military aid to help improve Azerbaijan's ability to guard its maritime borders.