A support vessel maneuvers near the crude oil tanker 'Devon' as it sails through the Persian Gulf towards Kharq Island oil terminal to transport crude oil to export markets in Bandar Abbas, Iran, on Mar. 23, 2018.

The United States has warned Hong Kong to be on alert for a vessel carrying Iranian petroleum that may seek to stop in the Asia financial hub, and said that any entity providing services to the vessel will be violating U.S. sanctions.

The news comes nearly a month after U.S. President Donald Trump's administration stepped up moves to choke off Iran's oil exports by scrapping waivers it had granted to big buyers of Iranian crude oil, including China.

The fully laden Pacific Bravo abruptly changed course on Monday to head towards Sri Lanka, according to shipping data on Refinitiv Eikon. The vessel had earlier identified Indonesia as its intended destination, according to ship-tracking data, but industry sources said it was most likely going to China.

The Pacific Bravo on Monday changed its automatic identification system (AIS) destination to Sri Lanka, where it meandered off the southern coast for a little more than a day, the ship-tracking data showed.

Late on Tuesday evening, the tanker sailed away from Sri Lanka towards the busy waterways of the Strait of Malacca, a key shipping lane towards East Asia, although its AIS destination was still set as Sri Lanka.

A ship's crew manually enters AIS destination settings, and there can be a delay in updates while the vessel is at sea.

"Anyone who does business with this ship, the Pacific Bravo, would be exposing themselves to U.S. sanctions," a senior U.S. official said on condition of anonymity.