An American THAAD missile defense system is now operational in South Korea, less than two months after its components arrived there, the U.S. military says.

The system is meant to protect South Korea from ballistic missiles fired by North Korea, the Pentagon says. But China and other critics of the move say it will only increase tensions on the Korean Peninsula. The decision to install the missile shield was made by the U.S. and South Korea last July.

The THAAD deployment has caused wide ripples on the peninsula, with North Korea saying the U.S. is antagonizing it and local residents protesting the installation.

Other concerns center on timing and politics.

"There's a presidential election here next week," NPR's Lauren Frayer reports from Seoul, "and the front-runner vows to renegotiate the U.S. missile defense deal. President Trump has also angered many South Koreans by saying Seoul should pay for it."

In another development, CIA Director Mike Pompeo arrived in South Korea for three days of meetings Tuesday, becoming the fourth high-level official from the Trump administration to visit (following Vice President Pence, Secretary of State Rex Tillerson and Defense Secretary James Mattis).

Pompeo began his visit by touring Yeonpyeong Island, which endured a deadly artillery and rocket attack by North Korea during a skirmish between the two countries in late 2010.

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