DARWIN, Australia — The port in this remote northern Australian outpost is little more than a graying old wharf jutting into crocodile-infested waters. On a recent day, there was stifling heat but not a ship in sight. “Our pissy little port,” as John Robinson, a flamboyant local tycoon, calls it.

The financially hurting government of the Northern Territory was happy to lease it to a Chinese company in October for the bargain price of $361 million, raising money for local infrastructure projects.

“We are the last frontier; you take what you can get,” said Mr. Robinson, who is known as Foxy. “The Northern Territory doesn’t have the money for development. Australia doesn’t have it. We need the major players like China.”

But the decision has catapulted the port of Darwin into a geopolitical tussle pulling in the United States, China and Australia.