At least four ships carrying copper are trying to reach U.S. ports before August to get ahead of planned import tariffs on the metal.

The shipments represent the final scramble by merchants to cash in on a lucrative arbitrage trade that has upended the global copper market since President Donald Trump first floated the idea of copper tariffs. The urgency to secure imports increased in the weeks since Trump announced the levy would be 50% starting August 1.

Bulk carrier Kiating left Australia’s Townsville port on July 16 carrying 8,000 metric tons of refined cargo and is destined to reach Hawaii by July 30, according to shipping data provider Kpler. The firm can’t identify who owns the cargo, but it said two other recent U.S.-bound shipments from the port contained copper from Glencore Plc’s Mount Isa Mines.

Port data show that the Kiating was originally scheduled to land in New Orleans, but changed its destination to Hawaii after Trump’s announcement — cutting its likely voyage time by almost 20 days. Even so, the cargo owner will be in a race against time to register the metal with the local customs office once the vessel arrives.

“It’s hard to say how efficient clearance will be in Hawaii, given that it’s such an atypical destination for this cargo,” said Ben Ayre, lead dry-bulk shipping analyst at Kpler.

In Latin America, three vessels brimming with Chilean copper are also rushing to get to U.S. ports. Cargo ship Louise Auerbach is near Colombia’s Buenaventura port and en route for a July 28 arrival at Tampa, Florida, according to data compiled by Bloomberg and people with knowledge of the voyage. The BBC Norway is in Panama and the BBC Campana is anchored off northern Chile’s coast, according to the latest shipping data.

The vessels are among the last batch of copper cargoes whose owners are betting they can clear U.S. customs just before the tariff bites. For reference, the difference between arriving ahead of the levy and having to pay it would be more than $70 million on a typical bulk carrier cargo of 15,000 tons. The voyage from northern Chile to southern U.S. takes 10 to 15 days.

To boost the chances of landing before the tariffs, shippers can attempt to clear customs for the entire cargo at their first U.S. port of call. They can also pay for preferential spots in the lineups, turning what can be days of waiting into just hours.

With copper prices surging in the U.S., traders including Glencore, Mercuria Energy Group, Trafigura Group, Hartree Partners LP and IXM SA have shipped huge volumes to U.S. ports since Trump ordered the Commerce Secretary in February to consider tariffs as part of an probe into the impact of foreign copper on the U.S.

The tariff trade allowed those firms to capture profits that industry veterans say are the biggest they’ve ever seen. A 50% copper tariff is double what many analysts and traders expected, and prices in New York surged even more after Trump’s July 8 tariff announcement, creating even bigger potential profits for traders who can get vessels to America in time.

With copper trading at about $9,900 a ton on the London Metal Exchange, a 50% levy would mean U.S. buyers need to pay a further $4,950 to customs authorities to import copper into the country. Nominally, traders stand to make nearly as much in profit if they can import the metal before the tariffs land in less than two weeks.

Traders are still awaiting key details about the tariffs, particularly whether there will be a grace period for cargoes that are already on the water — as there have been when similar levies were imposed on aluminum and steel.