US isolation at the United Nations over efforts to end renewed Middle East violence has seen China seize the chance to burnish its multilateral leadership credentials, diplomats say, just months after President Joe Biden declared: "America is back."

For the past week the United States - a strong ally of Israel - has repeatedly opposed a statement by the 15-member UN Security Council on hostilities between Israel and Palestinian militants in Gaza, leading China's Foreign Minister Wang Yi to publicly call out Washington for "obstruction."