LONDON, July 31 (Reuters) - Tariff-related price hikes may start to bite at the end of the third quarter as companies may by then have sold off U.S. stockpiles built up ahead of the new duties, according to the International Chamber of Commerce.

Businesses making everything from cars to drugs and cheese and wine have expedited deliveries to the United States this year to get ahead of U.S. President Donald Trump's tariffs.

They have about four months of inventory, about one month more than average, Andrew Wilson, International Chamber of Commerce deputy secretary general, estimated on Thursday, helping some delay hiking prices.

"You could expect it to bite at the end of Q3," he told Reuters once they have sold off that inventory. Wilson previously forecast tariff-related price hikes would show up in U.S. inflation in the fourth quarter or early next year.

Data on Thursday showed U.S. inflation increased in June as tariffs started raising the cost of some goods, supporting economists' expectations that price pressures would pick up in the second half.

Some of the world's biggest companies have warned for months that they would be squeezed by duties.

They have now started to outline how they plan to pass on the costs and change their businesses to try to cushion the blow of rising costs, uncertainty over U.S. trade policy, and waning consumer confidence.

Companies are testing how much they can pass tariffs onto U.S. customers.

But global retailers including sandal maker Birkenstock BIRK.N and jeweller Pandora PNDORA.CO have also looked at raising prices across multiple markets to avoid hurting U.S. sales.

"There's a logic taking hold that (price hikes) won't be just borne by the U.S. consumer," he said.

(Reporting by Josephine Mason; Editing by Susan Fenton)

((Josephine.Mason@thomsonreuters.com; +44 207 542 7695; Reuters Messaging: josephine.mason.reuters.com@reuters.net))