Venezuela accused the United States of hampering its diplomatic efforts on Thursday, saying Washington was denying airspace to its China-bound president and blocking visas for its UN delegation. In a fiery speech in the capital Caracas, Venezuelan President Nicolas Maduro bristled with outrage at the “serious offense” of denying his plane rights to American airspace over the Atlantic, and vowed his planned trip to Beijing this weekend would not be delayed. The leftist leader - hand-picked successor to the late anti-US firebrand leftist Hugo Chavez - also accused the US of refusing visas to some of the members of his delegation to the UN General Assembly next week. US officials did not immediately confirm or comment on the charges. Venezuela and the United States were often at odds during Chavez’s 14-year rule and relations have remained tense under Maduro. The two countries have not had ambassadors in each other’s capitals since 2010. Caracas said it had received word from US authorities that Maduro’s plane was denied rights to American airspace over the Atlantic. “We denounce this as another insult of North American imperialism against the government,” Foreign Minister Elias Jaua told reporters. “No one can deny airspace to a plane carrying a president on an international state visit. There is no valid argument to refuse airspace.” In his speech, Maduro said “denying permission to a head of state to fly over the airspace it colonised in Puerto Rico is a serious offense.” But he said his trip would not be delayed, as his plane could take a longer route. “We are not going to be stopped by the US government from going to China,” he added. Jaua, who is set to travel with Maduro to Beijing, expressed hope that US authorities would “rectify the error,” which he blamed on lower-level officials. Maduro said Washington has also denied visas to high level members of its UN delegation. “You are required to give visas to the whole Venezuelan delegation,” the Venezuelan leader said, without confirming whether he would now attend the meeting in person. “We will not accept that you deny a visa to Minister [Wilmer] Barrientos, nor to the head of the military, nor to any other member of the delegation,” he said, threatening diplomatic retaliation on a “more drastic level, if necessary.” Maduro also suggested the UN should move its headquarters out of the United States. The accusations quickly drew support from regional allies. Bolivian President Evo Morales called for an emergency meeting of regional leaders to propose “the immediate withdrawal of ambassadors to the US” in solidarity with Venezuela.