Maputo is now a magnet for companies aspiring to be significant South African coal exporters, following a Vitol joint venture deal, industry sources said.

The port has been used on a small scale for coal exports, which shippers were unable to move from the main export hub, Richards Bay Coal Terminal, but is now the centre of major expansion plans for South African coal.

Two exporters have in the last few months started using the main Maputo harbour, which has no loading equipment, for the first time and new fencing has been set up around stockpiles there, a recent visitor to the port said.

A handful of mining majors own RBCT, by far the cheapest, most efficient port, but new entrants have mostly failed to gain a foothold there.

"If you want to be producing South African coal for export, don't ever think you are going to get into Richards Bay - Maputo is really the only option," an executive involved in South African projects said.

Would-be entrants already see Glencore well established. At Maputo it accounts for a third of the 3million tons a year of exports and is also using the main harbour.

This deadlock has been frustrating for rival, large trading firms wanting to catch up with Glencore's roughly 20-year head start in building an integrated global coal business including investments in mines and ports and myriad offtake agreements.

"Glencore were in Matola (Maputo's inland coal terminal) from the start, to see how significant or useful an export point it was, with the ability to back out at any time," said an industry source, who recently returned from Maputo.

"Vitol seems to want to move into the Glencore space (by investing in ports and production)," a veteran South African industry source said.

"This is a great deal for Vitol; it gives them an export outlet for thermal, coking and sized coal and from the Waterberg, too, eventually," another industry source said.

If Glencore completes its purchase of Optimum Coal Holdings with its empowerment partner, entrepreneur Cyril Ramaphosa, it will be the country's fourth-largest exporter after Anglo American, and own a big chunk of highly desirable Richards Bay export capacity.