Secretary of State Antony Blinken on Wednesday reassured Philippine’s top diplomat in a phone call that the U.S. stands with Southeast Asian countries after recent acts by China in the region, a report said.

Reuters reported that Blinken told Teodoro Locsin, his Philippine counterpart, that the U.S. rejects Beijing’s claims to the South China Sea and only recognizes claims under international law.

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China ratcheted up activity in Taiwan airspace on Sunday by flying 15 fighter jets between mainland Taiwan and the Pratas Islands in the South China Sea, a report said.

Reuters, which cited Taiwan’s Defense Ministry, reported that the jets included six J-10 fighters, two SU-30s and other military planes. A day earlier, China flew eight bombers and four fighters into the same airspace, the report said.

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Blinken, said in a confirmation hearing Tuesday there is "no doubt" China poses the greatest threat of any nation to the U.S.  and the Trump administration was right to take a tougher stance against the Asian power. 

"President Trump was right in taking a tougher approach to China," said Blinken, who served as then-Vice President Biden’s national security advisor before being elevated to deputy secretary of state under Barack Obama. "Not the way he went about it in a number of ways, but the basic principle was right." 

Fox News' Morgan Phillips contributed to this report