By Wendell Roelf

CAPE TOWN, Feb 17 (Reuters) - South Africa could turn to Russia or Iran to expand its civilian nuclear power capacity, a senior government minister said, a stance analysts say could deepen a rift with the United States and further delay the renewal of a strategic energy pact.

South Africa, which operates Africa's only nuclear power plant, Koeberg, plans to add 2,500 megawatts of new capacity to tackle electricity outages that have plagued the economy and to reduce emissions.

"We can't have a contract that says Iran or Russia must not bid, we can't have that condition," Minister of Mineral and Petroleum Resources Gwede Mantashe, one of the government's leading proponents of expanding nuclear capacity, said.

"If they are the best in terms of the offer on the table, we'll take any (country)," he told Reuters.

The country is under scrutiny from Washington after President Donald Trump issued a far-reaching executive order this month halting aid. Among other criticisms, the order claimed - without providing evidence - that South Africa was "reinvigorating its relations with Iran to develop commercial, military, and nuclear arrangements".

Pretoria has no bilateral cooperation with Iran on nuclear power or any nuclear-related technology, the office of South African President Cyril Ramaphosa said.

A U.S. State Department spokesperson did not comment on the possibility of Iran or Russia helping South Africa expand its civilian nuclear capacity.

A South African tender for nuclear projects, initially planned for last year, has been delayed for further consultation following legal challenges led by the then opposition Democratic Alliance party, now part of the coalition government.

ALMOST A DECADE OF TALKS

Pretoria and Washington had been seeking to conclude after almost a decade of talks a new civilian nuclear pact, known as a Section 123 Agreement, a prerequisite for exporting U.S.-made nuclear fuel or equipment.

"The allegations made in the executive order can significantly complicate getting the agreement renewed," said Isabel Bosman, a nuclear energy researcher at the South African Institute of International Affairs.

The State Department spokesperson did not comment on whether Trump's executive order would affect talks between the two countries.

The previous 123 agreement, implemented in 1997, lapsed in December 2022.

Negotiations for a new agreement have already been finalised at a technical level but nothing is signed yet as legal processes on both sides were incomplete, Zizamele Mbambo, a senior official in South Africa's energy ministry said.

"As far as we know both sides remain firmly committed to conclude this new agreement," he added.

Failure to secure a new deal could block South African power utility Eskom from sourcing reactor fuel from Westinghouse for Unit 1 at Koeberg, industry analysts say. Unit 2 is supplied by France's Framatome.

It may also hinder U.S. companies, such as the Bill Gates-backed TerraPower and ASP Isotopes ASPI.O, from investing in South Africa during a global atomic renaissance, the analysts added.

(Reporting by Wendell Roelf; additional reporting by Timothy Gardner in Washington; editing by Joe Bavier and Emelia Sithole-Matarise)

((wendell.roelf@thomsonreuters.com; +27 21 461 3523;))