WASHINGTON (Reuters) - The United States is asking allies to stop domestic companies from servicing certain chipmaking tools for Chinese customers, a U.S. commerce department official said on Wednesday, as it ramps up efforts to hobble China's chipmaking capabilities.

"We are working with our allies to determine what is important to service and what is not important to service," said export controls chief Alan Estevez, speaking to reporters at an annual conference.

"We're pushing for not servicing of those key components and these are discussions we are having with our allies."

Washington has been locked in a years-long technology war with Beijing, seeking to stop China from making more advanced chips that could be used to strengthen its military.

The Biden administration announced new restrictions on shipments of American-made chipmaking tools to advanced Chinese chip factories in 2022, and convinced key chipmaking tool producers Japan and the Netherlands to follow suit with their own controls.

The U.S. rules made it difficult for U.S. companies to continue servicing tools that Chinese firms bought prior to the new regulations, but the Dutch and Japanese rules did not include similar restrictions.

That has spurred U.S. officials to convince allies to mirror U.S. curbs.

(Reporting by Alexandra Alper and Karen Freifeld; editing by Costas Pitas)