The Trump administration on Thursday announced new limits on the sharing of civilian nuclear power technology with China, export controls U.S. officials said were warranted in response to theft of American nuclear technology and intellectual property for military and other purposes.

The new national security measures, which are effective immediately, may cause American nuclear developers some pain in the short term, U.S. officials acknowledged during a conference call with reporters. But they said the restrictions were necessary because of national security and economic concerns. The officials spoke on the condition that they not be identified.

“The United States cannot ignore the national security implications of China’s efforts to obtain nuclear technology outside of established processes of U.S.-China civil nuclear cooperation,” Energy Secretary Rick Perry said in a statement.

Under the policy, which came after a review that also included the Departments of Defense and State and the FBI, there will be a “presumption of denial” for new license applications or extensions to existing authorizations related to the China General Nuclear Power Group, which was indicted on charges of conspiring to steal American nuclear technology.

A similar policy will be in place for exports involving some types small modular reactors and other new nuclear technology under development in the U.S. The regulations, however, appear to exempt a small modular reactor design under development by Flour Corp.’s NuScale Power LLC.

The suspension of licenses to related to CGN Power likely dashes Westinghouse Electric Co.’s hopes of expanding its presence in China beyond the four nuclear reactors already scheduled,” according to James Grant, a junior fellow with the American Foreign Policy Council.

“This announcement effectively kills Westinghouse’s chance to compete with the likes of Russia’s Rosatom, France’s Areva, or China’s own domestic Hualong One design,” Grant said in an email. In addition, if the new measures prevent Westinghouse from delivering fuel to China “it will be a major blow to the company,” one of the largest global sellers of nuclear fuel, Grant added.

American nuclear companies face uncertainty, said Henry D. Sokolski, executive director of the Nonproliferation Policy Education Center in Washington.

“Anybody who is in the nuclear exports business trying to market to China cannot be happy about this. There is not much silver lining here,” Sokolski said in a phone interview. “This regulation opens the door to the consideration of the national security considerations of any nuclear energy export that wasn’t explicitly called for before.”

Westinghouse Electric spokeswoman Sarah Cassella declined to comment on the Energy Department announcement. Messages left with NuScale were not immediately returned.

China is the most active nuclear market with 13 reactors under construction, according to Bloomberg New Energy Finance.