GENEVA - The United States, which closed its borders to much of the world as the pandemic took hold, said Wednesday it plans eventually to begin allowing fully vaccinated foreigners back in, while China tightened overseas travel curbs amid surging infection numbers. The two countries’ travel-related moves come as the fast-spreading Delta variant cuts a deadly swath across the planet, not only affecting movement between countries but also the northern hemisphere’s summer tourist season. Recognizing the importance of international travel, a White House official said in a statement that the US administration wants to reopen to visitors from abroad in a “safe and sustainable manner,” though without specifying a timeframe. Reopening is to include the development of “a phased approach that over time will mean, with limited exceptions, that foreign nationals traveling to the United States -- from all countries -- need to be fully vaccinated,” the official said. Meanwhile in China, which had previously boasted of its success in crushing Covid-19 after it first emerged there in December 2019, mass testing campaigns have uncovered Delta variant infections across the country. China’s immigration authority announced it would stop issuing ordinary passports and other documents needed for exiting the country in “non-essential and non-emergency” cases.