Missouri Republican Sen. Josh Hawley became the first senator to oppose adding Sweden and Finland to the North Atlantic Treaty Organization (NATO), writing in an op-ed that doing so would prevent the U.S. from effectively combating China.

Sweden and Finland both announced in May that they would seek to join the 73-year-old defense organization in the aftermath of Russia’s invasion of Ukraine. NATO formally invited the two previously neutral nations into the alliance in late June, after Turkey dropped its objection to their joining. The Biden administration has promised to “send a very clear message” if Russia attempts to prevent the two countries from joining, with National security adviser Jake Sullivan saying that the U.S. “will not tolerate any aggression.”

“When it comes to Chinese imperialism, the American people should know the truth: the United States is not ready to resist it. Expanding American security commitments in Europe now would only make that problem worse—and America, less safe,” Hawley wrote Monday in The National Interest. “Confronting this threat will force us to make tough choices.”

Hawley described the two countries’ desire to join NATO as “totally understandable.” Nevertheless, he added, “the United States cannot defeat China and Russia in two major wars at the same time,” a situation made more likely by expansion.

Why I Won’t Vote to Add Sweden and Finland to NATO https://t.co/YPUvgYz8Xr

— Josh Hawley (@HawleyMO) August 1, 2022

The Senate Foreign Relations Committee voted 21-0 June 14 to support a resolution approving Sweden and Finland’s joining, with Republican Kentucky Sen. Rand Paul voting “present.” Paul previously voted against North Macedonia’s entrance into NATO in 2019, a move Hawley supported. (RELATED: ‘Recipe For Disaster’: Rand Paul Defends Blocking Ukraine Military Aid Package, Takes Shot At John McCain)

The resolution passed the House of Representatives 394-18 on July 18. Treaties must be approved by two-thirds of the Senate to go into effect.

Hawley pointed to NATO guidelines requiring that member countries contribute at least two percent of their gross domestic product to defense spending. Sweden does not expect its defense spending to reach two percent of GDP until 2028, and Finland’s defense spending reached two percent for the first time in 2022.

“In the event of a future conflict in Europe, U.S. forces would almost certainly be called in to defend both countries,” Hawley wrote. “U.S. resources are not unlimited. Already we spend the better part of a trillion dollars a year on defense. And our manpower is already stretched thin across the globe.”