ANKARA, (Reuters) – Turkey’s energy minister goes to Iran on Saturday to work out the details of a major gas deal launched last month and should also agree a separate plan to build power stations in both countries, an energy official said.

Turkey has agreed to invest $3.5 billion in Iran’s gas fields from next year, and signed a preliminary deal to use Iran as a transit route for Turkmen gas and to develop Iran’s South Pars gas field to take gas to Europe, officials have said.

The deal envisages exports of 30 billion cubic metres of gas from Iran and Turkmenistan a year to European markets and is expected to be finalised in 4-6 months.

A team of Turkish energy officials travelled to Iran at the start of this week.

Separately, Energy Minister Hilmi Guler is expected to sign a memorandum of understanding to build “high capacity” thermal and hydroelectric plants on both sides of the Iran-Turkey border, the official from the ministry said.

Iran is import-dependent Turkey’s second-biggest gas supplier after Russia.

The United States, which has no diplomatic ties with Iran, has voiced its opposition to the initial gas deal between Turkey and Iran.