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Chuck Schumer, the leader of the US Senate, on Monday told Chinese President Xi Jinping that Beijing should condemn the Hamas attacks against Israel.
Mr Schumer said he was "very disappointed" by a statement from China's Foreign Ministry on Sunday on the escalating violence between Israel and Gaza.
“I urge you and the Chinese people to stand with the Israeli people and condemn the cowardly and vicious attacks upon them,” Mr Schumer told Mr Xi in Beijing, where a bipartisan group of US congressional leaders are on their first visit to the country in eight years.
The top Senate Democrat also criticised Chinese Foreign Minister Wang Yi for showing “no sympathy or support for Israel during these tough, troubled times.”
"I say this with respect but I was disappointed by the Foreign Minister's statement that showed no sympathy or support for the Israeli people during these troubled times," Mr Schumer told Mr Xi.
Asked about Mr Schumer's remarks, Foreign Ministry representative Mao Ning said China was "highly concerned" about the escalation.
"We are very saddened by the civilian casualties caused by the conflict and also oppose and condemn such acts against civilians," she said.
Ms Mao said China was calling for a ceasefire to avoid more deaths.
Taking a hardline on China has become one of the few bipartisan areas of consensus in Washington in recent years, with Congress often being a driving force for tougher policies on Beijing. The delegation to China was led by Mr Schumer, a Democrat, alongside Mike Crapo, a Republican senator.
Mr Wang told the senators he hoped their visit would help get US-China relations back on track.
Mr Schumer told Mr Xi the main purpose of the visit was to ensure “economic reciprocity”. Before arriving in Beijing, the US politicians met American business leaders in Shanghai and discussed issues involving fair competition.
“We feel that China must also provide a level playing field for American companies and workers,” Mr Schumer said he told Mr Xi.
“Most Americans, our bipartisan delegation included, do not believe we have that fairness now.”
Last month, the American Chamber of Commerce in Shanghai reported optimism among US firms was at historic lows, citing “concerns about geopolitics, US-China relations and China’s poor economy” as weighing on expectations.