Talking to Tasnim News Agency, Deputy Oil Minister and Managing Director of National Iranian Gas Company (NIGC) Hamidreza Araqi said Tehran and Ashgabat have brought lawsuits against each other, saying the international arbitration court is hearing the two cases.
Iran filed a complaint against Turkmenistan's move to halt gas exports in wintertime, while the Turkmens have complained about financial issues, he added.
Turkmenistan cut off gas supplies to Iran in winter 2016, saying Iran should clear its outstanding debts.
Iran has imported natural gas from Turkmenistan since 1997 for use in the north of the country, which is furthest from the gas resources in the south.
In August 2017, Iran started to construct a new gas pipeline stretching from the northern city of Damghan in Semnan Province to Neka in Mazandaran Province.
Officials say the pipeline will cut Mazandaran Province's dependence on imports from Turkmenistan.