China claims 90 percent of the South China Sea, which is believed to be rich in oil and gas, its claims overlapping with those of Brunei, Malaysia, the Philippines, Vietnam and Taiwan.

Recent satellite images suggest China has made rapid progress in filling in land in contested territory in the Spratly islands and in building an airstrip suitable for military use and that it may be planning another.

"As China seeks to make sovereign land out of sandcastles and redraw maritime boundaries, it is eroding regional trust and undermining investor confidence," Blinken said on Wednesday.

"The U.S. assumptions are groundless," ministry spokesman Hong Lei told a regular briefing. Blinken said the previous day that competing claims had to be handled "diplomatically".
"We don't take sides but we strongly oppose actions that aim to advance a claim by force or coercion," he said.

"We will continue to encourage all claimants to resolve their differences in accordance with international norms."

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