Joe Biden is using the first visit to Angola by a U.S. president to promote billions of dollars of investments in the sub-Saharan African nation.

Joe Biden pledged lasting U.S. engagement with Africa as he met his Angolan counterpart Joao Lourenco in Luanda on Tuesday, as part of his first and only visit to sub-Saharan Africa as U.S. president.

The project aims to advance the U.S. presence in a region rich in cobalt, copper and other critical minerals used in batteries for electric vehicles, electronic devices and clean energy technologies. By the end of the decade, the rail line could even go a long way toward linking southern Africa's western coast with the continent's eastern edge.