By Tim Reid and Gram Slattery

Former Vice President Mike Pence said China is close to becoming an "evil empire" on Monday as he and fellow Republicans vying for their party's presidential nomination ramp up rhetoric against what they say is America's number one foreign adversary.

"China is the greatest strategic and economic threat facing the United States in the 21st Century," Pence said in a speech at the conservative Hudson Institute in Washington.

"China may not yet be an evil empire – but it is working hard to become one," Pence said.

Pence called for increased arms sales to Taiwan, breaking off U.S. economic ties with essential Chinese industries, restricting Chinese nationals working in U.S. technological companies to reduce intellectual property theft, and a nationwide ban on Chinese-owned TikTok social media.

The Republicans campaigning to become the party's pick for the November 2024 election are almost in unanimous agreement: China is the leading foreign foe of the U.S.

In this Republican race, the attacks are more frequent and the proposals bolder, political operatives said, thanks to a shift in U.S. public opinion.

Some 50% of Americans identify China as the greatest threat to the United States, according to a Pew Research poll released in late July. Russia is next, according to 17% of respondents.

Vivek Ramaswamy, a tech investor in the race, is due to deliver a speech on Thursday in which he will lay out his plan for securing economic independence from China.

Fellow rival and Florida Governor Ron DeSantis is also due to give a foreign policy speech soon, his aides said. In it, he is expected to lay out an aggressive stance towards China. DeSantis has already called for ending normal trade relations with China. In Florida, he has banned TikTok from government and school-issued devices.

In his speech, Pence amplified a split within the Republican candidates over the war in Ukraine, and how China will view the continued U.S. response to Russia's invasion of its neighbor.

Pence said it was vital the U.S. gives all military support necessary to Ukraine so it can defeat Russian forces.

Without naming them, Pence decried what he called the "isolationism" of some 2024 rivals - such as Ramaswamy, DeSantis and former President Donald Trump - who have questioned unchecked military and economic support for Ukraine.

"Consider what would happen if the Republican appeasers are successful in pulling support for Ukraine," Pence said. "What message would it send to China, except a giant, flashing green light for the Chinese invasion of Taiwan."

China, which claims democratically governed Taiwan as its own territory, has increased its military activities near the island in recent years in response to what Beijing calls "collusion" between Taiwan and the United States.

(Reporting by Tim Reid and Gram Slattery, editing by Ross Colvin and Grant McCool)