Mexican President Andres Manuel Lopez Obrador on Wednesday again declined to congratulate Joe Biden for winning the U.S. presidential election, making him stand out increasingly among world leaders who have withheld their recognition. Speaking shortly after China’s President Xi Jinping congratulated Biden for his victory, Lopez Obrador reiterated that it would be wrong to offer congratulations until the electoral process has been formally concluded. “We do not agree with offering congratulations in advance,” Lopez Obrador told reporters at a regular government news conference. “What’s the best thing? For us to wait.” U.S. President Donald Trump, a Republican, has launched legal challenges in an effort to overturn the election result, accusing Biden’s Democrats of trying to steal the election. However, without conceding defeat, he has now signaled that transition to a Biden administration can proceed. Lopez Obrador, who has repeatedly accused opponents of electoral fraud over the years, again referred to the 2006 Mexican presidential election by way of justifying his stance. Lopez Obrador insists he was robbed in 2006. His use of that example in defending his stance on Biden has upset some U.S. officials, who regard the comparison as inappropriate. The Mexican president said he had nothing against any candidate or political party in the U.S. electoral process. Privately, Mexican officials say he is wary of antagonizing Trump, who during his presidency threatened to hurt Mexico economically if it did not curb illegal immigration. The Mexican president said some in his security cabinet suggested in a meeting on Tuesday that it was time to recognize Biden. A number of U.S. Democrats have expressed frustration with Lopez Obrador’s reluctance to recognize Biden, and one former official of the last Democratic administration said the Mexican president’s stance was starting to look “foolish.” “The world is moving on,” said the ex-official, who spoke on condition of anonymity, noting that other countries were moving ahead with their business with the incoming Biden administration. “Mexico is getting left behind,” said the former official. “But that’s Mexico’s fault.”