FILE PHOTO: Argor-Heraeus' CEO Robin Kolvenbach holds one kilo bars of silver and gold at the plant of refiner and bar manufacturer Argor-Heraeus in Mendrisio, Switzerland, July 13, 2022. REUTERS/Denis Balibouse/File Photo

LONDON (Reuters) -Some gold refineries, including a large Swiss entity, have paused deliveries of bullion to the United States due to uncertainty over whether country-specific U.S. import tariffs will apply to their metal, two sources familiar with the matter told Reuters.

According to a ruling on the U.S. Customs and Border Protection service's website on Friday, Washington may place the most widely traded gold bullion bars in the United States under country-specific import tariffs, a move that would roil the metal's global supply chains.

The ruling refers to cast gold bars from Switzerland, the world's biggest bullion refining and transit hub, which is now subject to U.S. import tariffs of 39%.

The CBP said that the correct HS customs code to use when supplying 1 kg bullion bars and 100 troy ounce bullion bars, the most traded sizes in the U.S. futures market, to the U.S. would be 7108.13.5500 and not 7108.12.10.

However, Washington included only the latter code in the list of products excluded from country-specific import tariffs in April, with 7108.13.5500 not on the list.

The CBP did not immediately reply to a Reuters' request for further comment.

The Swiss Association of Precious Metals Manufacturers and Traders (ASFCMP) said in a statement that the clarification did not apply exclusively to Switzerland but to all 1 kg and 100 ounce gold cast bars imported into the U.S. from any country.

"The United States is a longstanding market for us, so this is a blow for the industry and for Switzerland," Christoph Wild, president of the ASFCMP, told Reuters.

"With a tariff of 39%, exports of gold bars will be definitely stopped to the U.S," Wild said.

While Switzerland is the refining and transit hub, Britain is home to the world's largest over-the-counter gold trading hub, and South Africa and Canada are among major gold miners.

"Likely imposing 39% tariffs on Swiss kilobars is akin to pouring sand into an otherwise well-functioning engine. I say "likely"...the possibility remains that this is an error," said independent analyst Ross Norman.

A major gold refinery in Switzerland has stopped deliveries to the U.S. for now, a top manager at the refinery told Reuters, while a gold logistics specialist said some other industry players outside Switzerland had also paused deliveries.

U.S. gold futures were last up 0.9% at $3,484 per ounce, widening a premium over spot gold, the global benchmark, which fell 0.4% to $3,384.

The muted reaction may be explained by high stocks of gold in Comex-owned warehouses, after massive inflows over December-March as traders hedged against the possibility of broad U.S. tariffs hitting bullion imports.

"The COMEX inventories currently amount to 86% of open interest - against a more normal 40-45% - so there is no liquidity issue at present," said StoneX analyst Rhona O'Connell.

The CBP could still amend its view, or Washington could possibly add the second HS code to its list of exclusions, or the industry could challenge the CBP's stance, the logistics source added.

(Reporting by Polina Devitt;Additional reporting by John Revill;Editing by Veronica Brown, Louise Heavens and Sharon Singleton, Kirsten Donovan)