The U.S. sent two nuclear-capable B-52H bombers over the South China Sea on Wednesday, marking the second time this month that the bombers flew over the region.

Such Air Force missions are often derided by China, which says the U.S. is needlessly causing tension between the countries.

The flights to the South China Sea came just weeks after U.S. Secretary of State Mike Pompeo assured the Philippines that the United States will come to its defense in the event of a conflict in the South China Sea.

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“Two B-52H Stratofortress bombers took off from Andersen Air Force Base, Guam, and conducted routine training in the vicinity of the South China Sea on March 13, 2019 [Hawaii Standard Time], before returning to base,” Pacific Air Forces said in a statement Friday, the Stars and Stripes reported.

The last mission was on March 4, when one bomber flew over the South China Sea during a joint military drill with the Japanese air forces. That flight was the first mission reported since last November, though some missions aren’t disclosed, according to the outlet. Stars and Stripes reported that the recent flights were part of “routine training” in the region.

“U.S. aircraft regularly operate in the South China Sea in support of allies, partners, and a free and open Indo-Pacific,” the PACAF statement noted. “U.S. Pacific Air Forces bombers have flown from Guam for more than a decade as part of U.S. Indo-Pacific Command’s continuous bomber presence operations.”

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U.S. Indo-Pacific Command chief Adm. Philip Davidson reportedly said last week that there was a rise in the activity by the Chinese military in the region over the last year, the Japan Times reported.

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“It’s building, it’s not reducing in any sense of the word,” Davidson was quoted as saying. “There has been more activity with ships, fighters and bombers over the last year than in previous years, absolutely.”

Fox News’ Lucas Tomlinson contributed to this report.