South Africa’s biggest labour union federation urged local shareholders, including the powerful Public Investment Corporation (PIC), to oppose BHP Group’s bid to buy Anglo American.

The Congress of South African Trade Unions (Cosatu), which includes the National Union of Mineworkers (NUM) among its members, said a deal wouldn’t be in the national interest. South African shareholders hold about 26% of Anglo, with the PIC owning 8.4%, according to data compiled by Bloomberg.

BHP’s proposal to acquire Anglo on April 25 raised the ire of some members of South Africa’s government, including Mines Minister Gwede Mantashe. The Australian company responded by deploying a senior team including its chief executive officer to South Africa to win over government officials, regulators and local Anglo shareholders.

BHP’s proposal includes a plan for Anglo to spin off its Johannesburg-listed platinum and iron ore units before an eventual takeover of the remaining assets. Anglo, founded in Johannesburg in 1917, also owns manganese and diamond mines in South Africa. While the miner was the bedrock of the South African economy for decades, it shifted its headquarters to London in the late-1990s.

Anglo rejected the initial bid, but BHP is expected to make an improved offer, Bloomberg has reported. The PIC, which manages the pensions of government workers, has said it will assess any BHP offer.

“Cosatu is deeply concerned about the possible sale of Anglo assets in South Africa to BHP,” the union federation said in comments sent to Bloomberg on Tuesday. “It is critical that South African shareholders, including the PIC, ensure these assets remain South African-owned.”

BHP has said that under its offer, Anglo’s controlling interests in Kumba Iron Ore and Anglo American Platinum would be distributed to the company’s investors. That would give Anglo shareholders direct access to those companies’ dividends and future value, while allowing them to calibrate their exposures to those businesses, it said.

Cosatu is a key ally of South Africa’s ruling African National Congress (ANC) and President Cyril Ramaphosa was a co-founder of the NUM. The bid from BHP comes before a national election later this month, which could see the ANC lose its majority for the first time since winning power in 1994.

The presidency has rejected the premise that BHP’s approach is vote of no-confidence in South Africa, after the opposition presented the bid as a stinging rebuke of the government’s handling of the economy in a country with one of the world’s highest unemployment rates and deteriorating infrastructure.

“These companies were built on the back of South African mine workers and pension funds,” Cosatu said. “The profit they generate is needed to grow the economy and create decent jobs.”

BHP is targeting Anglo for its South American copper mines, which would make it the world’s biggest producer of the key metal.

Anglo’s South African operations have been hamstrung by fractious labor relations, power outages and the deterioration of the national freight rail company. Its Kumba unit has had to stockpile the steelmaking raw material because there aren’t enough trains to take it to a port.