Rouhani said Iran had a "serious will" to step up ties with the former Soviet state following a meeting with Kazakhstan's President Nursultan Nazarbayev.
"Iran is one of our most important international partners in its capacity as a peaceful neighbour along the Caspian Sea shore," Nazarbayev said.
A wide array of Western sanctions imposed over Iran's nuclear programme, most of them financial, are considered to have wrecked Tehran's economy in recent years.
Nazarbayev said talks had also looked at "easing banking contacts" between the countries and transport projects aimed at boosting bilateral trade set to reach around $1 billion (775 million euros) this year.
The Iranian leader is on a five-day tour of the region that also includes a leg in Tajikistan.
Rouhani will attend a heads of state summit for the regional Shanghai Cooperation Organisation in Dushanbe that looks set bring him face-to-face with Russian President Vladimir Putin and Chinese leader Xi Jinping.