BEIJING, July 17 (Reuters) - China's President Xi Jinping told former Philippine President Rodrigo Duterte to continue to promote cooperation between the two countries, after bilateral relations cooled with Duterte's successor seeking closer ties with Washington.

Ferdinand Marcos Jr was elected as president for a six-year term in 2022, taking over from Duterte who had adopted a more pro-China stance.

"I hope you will continue to play an important role in the friendly cooperation (between China and the Philippines)," state media cited Xi as saying during a meeting at the Diaoyutai state guest-house in Beijing on Monday.

Under Marcos, relations between China and the Philippines have grown tense, with Manila pivoting back to its traditional ally, the United States.

The Philippines and the U.S reaffirmed a decades-old security alliance during a trip by Marcos to the U.S. in May, where he met with President Joe Biden, who said the U.S. commitment to defending its ally was "ironclad".

Washington has pledged to defend the Philippines, which allowed the U.S. access to four additional military bases this year, angering Beijing.

Marcos also said granting U.S. access to the bases was a defensive step that would be "useful" if China attacked democratically governed Taiwan, which China claims as part of its territory.

China has always insisted on being friendly with its neighbours, which it sees as its partners, Xi said, without commenting on the state of current bilateral ties.

"During your tenure as president of the Philippines, you had resolutely made the strategic choice to improve relations with China in an attitude of being responsible to the people and to history," Xi told Duterte.

Last month, Duterte told domestic media that the Philippines could become a "graveyard" if it gets caught up in U.S.-China tensions.