The Chinese state news media reacted with cautious optimism to former Vice President Joseph R. Biden Jr.’s victory in the United States presidential election, expressing hope that he would stabilize the fast-deteriorating relations between the two countries.

But many outlets also continued to warn of future tensions between the superpowers, and to suggest that American democracy was in decline.

Under President Trump, trust and cooperation between the United States and China ebbed to their lowest levels in recent history, as a trade war raged and officials on both sides hurled recriminations about espionage, protest movements and the coronavirus pandemic. China’s state-controlled news outlets had criticized Mr. Trump and the United States with increasing stridence in recent months.