The United States will provide more funds for the construction of the Lobito Corridor, a rail link to export metals from Central Africa's Copperbelt, including a link for Zambia, US energy envoy Amos Hochstein said.

US has been supporting the project linking mineral-rich Democratic Republic of Congo (DRC) and Zambia to Lobito port in Angola.

The link seeks to bypass logistics bottlenecks in South Africa that have held up copper and cobalt exports - metals vital to the energy transition away from fossil fuels.

In 2022, a consortium led by global commodities giant Trafigura, Portugal's Mota-Engil and Vecturis SA of Belgium was awarded a 30-year concession for railway services and support logistics on the Lobito Corridor.

The consortium plans to spend $455 million in Angola and $100 million in the DRC on equipment, operations and infrastructure maintenance. Additional funding is required to extend the 1,700 km line into Zambia in the second phase.

"We have committed to finance $250 million for the Angola phase one. I expect that we will commit additional resources in the same range for the second phase," Hochstein said late Wednesday in an interview ahead of an investment forum on the project in Zambia.

The first phase involved upgrading the rail line on the Angolan side, and the second phase will involve building a new multibillion-dollar rail through Zambia and beyond, he said.

"I expect that we will start seeing some significant volumes using the rail by June-July," he said, without giving figures. The US and its partners have also mobilised close to $1 billion to expand the Lobito Corridor by developing a new 800 km rail line to further connect Zambia to the network, he said during the opening of the investment forum on Thursday.

"With the Africa Finance Corporation (AFC) as the private-sector lead developing the project, we aim to break ground in 2026 and have an operational rail between eastern Angola across Northwestern Zambia by 2028," he said.

The AFC had financing commitments from the US, the European Union and African Development Bank (AfDB), which would bring in extra private sector financing, he said.

Hochstein welcomed the announcement on Wednesday by mining firm Ivanhoe Mines that it had signed up to use the rail line for its copper exports from the DRC.

"That's critically important because it shows commitment by the private sector to this project. It will also make financing cheaper," Hochstein said.

He also said the US was contemplating other similar projects in Africa and elsewhere.

"Within Africa, I expect to have at least one more in the next year," Hochstein said, without specifying where.