"Be careful" because Beijing is "making Boeing build this massive plant in China" in order to secure orders, Trump warned.

Should Boeing, which has a major plant in South Carolina, launch operations in the Asian giant as it announced last year that it would, it's "bye-bye to South Carolina," he told an exuberant crowd at a rally in North Augusta.

"It won't happen if I'm president, by the way." Trump played up his international business acumen at a rally in North Augusta ahead of Saturday's Republican primary, the third statewide contest in the long road to the nomination.

But he and his rivals, including Ted Cruz, Marco Rubio and Jeb Bush, also traded political punches and laid out attack lines ahead of the crucial primary, the first in the US South.

First-term Senator Rubio, mindful of the large evangelical population in the state, told a townhall in Beaufort yesterday that his faith would help guide his decisions in the Oval Office.

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