MANILA, April 30 (AFP) - Philippine President Ferdinand Marcos left Manila on Sunday for a visit to the United States as he seeks to bolster ties with Washington amid growing tensions with China in the disputed South China Sea.

Marcos's visit comes as the United States had called on Beijing to stop "provocative and unsafe conduct" in the disputed waterway after a recent near-collision with a Philippine coast guard vessel.

Marcos begins his four-day trip with a meeting with US President Joe Biden on Monday at the White House, which the Philippine leader described as "essential to advancing our national interest and strengthening that very important alliance".

"We will reaffirm our commitment to fostering our long standing alliance as an instrument of peace and as a catalyst of development in the Asia Pacific region," Marcos said in a pre-departure statement. His plane took off at around 1:43 pm in Manila (0543 GMT), according to the Presidential Communications Office.

Ahead of Marcos's visit, US State Department spokesman Matthew Miller slammed China over the near collision of one of its coast guard ships with a Philippine patrol boat a week ago, saying it was a reminder of Beijing's "harassment and intimidation" in the contested waterway.

"We call upon Beijing to desist from its provocative and unsafe conduct," he said in a statement, adding that any attack on Philippine armed forces would trigger a US response.

Biden has been working to bolster relations with Asian allies as the US-Chinese relationship remains in a historically deep chill, and the Philippines' proximity to key sea lanes and Taiwan gives it particular strategic importance.

The near-miss on April 23 off the Spratly Islands was the latest in a long string of maritime incidents between China and the Philippines.

Beijing claims sovereignty over almost the entire South China Sea, ignoring an international ruling that its assertion has no legal basis.