Iran, Azerbaijan and Turkmenistan signed a trilateral gas swap deal Sunday for up to 2 billion cubic meters per year.

The much-awaited agreement was signed on the sidelines of the Economic Cooperation Organization (ECO) summit in the Turkmen capital Ashgabat by the oil ministers of the three countries in the presence of the presidents of Iran and Turkmenistan and prime minister of Azerbaijan.

Iran's Oil Minister Javad Owji, who was accompanying President Ebrahim Raisi to the ECO Leaders Summit, told reporters that under the swap deal, Iran will receive gas from Turkmenistan and deliver an equivalent amount to Azerbaijan.

Turkmenistan will sell 5 to 6 million cubic meters of gas per day to Azerbaijan through Iranian territory.

The deal is expected to be implemented in less than a month, before the winter sets in.

Speaking to reporters after the deal was signed, Raisi said it will "strengthen ties" between the three countries, which experts see as a sign of de-escalation in tensions between Tehran and Baku.

Iranian government spokesman Ali Bahadori Jahromi in a tweet late Sunday said the gas that Iran will receive under the agreement will cater to the needs of at least five provinces of the country.

In a swipe at the previous government, he said the "field of foreign relations is no longer limited to a few specific countries."

The gas swap deal comes a week after Iran and Azerbaijan agreed to push ahead with multiple energy agreements, including swap deals and joint development of oil and gas fields in the Caspian Sea.

The announcement came during a meeting between Owji and Azerbaijan's Deputy Prime Minister Shahin Mustafayev during the latter's visit to Tehran.

On the sidelines of the ECO summit, the long-running dispute between Tehran and Ashgabat over gas debt also came up.

Iran's oil minister assured his Turkmen counterpart that the first installment would be paid "soon,” without specifying the amount. According to reports, Iran owes Turkmenistan around $1.8 billion in payments for gas delivered to Tehran.

Although Iran has natural gas fields in southern parts of the country, it has been importing gas from Turkmenistan since the late 1990s to meet growing demand, especially in its northern provinces.