Liz Truss’s planned meeting with Joe Biden in Downing Street, which was to be her first major diplomatic event as prime minister, has been rescheduled for Wednesday at the UN. Officials from both countries said that a meeting in the margins of the UN general assembly would allow “fuller” bilateral discussion and was not the result of friction. But, whenever the two leaders meet, they face disagreements over Northern Ireland. “We have been in constant touch with Downing Street and have both decided that it is preferable to hold a full bilateral meeting in New York on Wednesday,” an administration official said. Biden and Truss will find plenty of common ground in pursuing a tough line on Russia for its invasion of Ukraine and on containing Chinese expansionism. But policy on Northern Ireland is a major irritant in the US-UK relationship. The protocol is an agreement with the EU after Brexit by which there are customs checks on goods transported from the British mainland to Northern Ireland, thus allowing the border between north and south to remain open and frictionless, a vital element of the 1998 Good Friday peace agreement. The Biden administration has already warned that any unilateral steps to undo the Northern Ireland protocol would not be “conducive” to a US-UK trade deal, and the president, who is proud of his Irish roots, is expected to make clear his personal commitment to defending the Good Friday agreement, and urge Truss to keep negotiating with Brussels. “Folks here are watching and [they] care,” a senior US official said. “Truss continues to say she wants a negotiated agreement. So let’s do it.” Arguing that the protocol is too much of a burden on British business, Truss has proposed to unilaterally negate parts of the agreement, and is contemplating invoking article 16 which allows a party to the agreement to suspend part or all the protocol if it causes “serious economic, societal or environmental difficulties”. The protocol is also likely to be included in her talks on Sunday with the Irish taoiseach, Micheál Martin, part of a hastily arranged diplomatic round as representatives from almost all the world’s 195 countries, including 100 presidents, gather for the Queen’s funeral. Truss hosted the Australian prime minister, Anthony Albanese, and New Zealand’s leader, Jacinda Ardern, at Chevening, her official residence in Kent, on Saturday. The meetings were framed by Downing Street as chats. She will also meet Poland’s president, Andrzej Duda, and Canada’s prime minister, Justin Trudeau, at No 10 on Sunday. The choice of who to meet allows the new Truss government to send signals about her priorities. Her choices emphasise the English-speaking Five Eyes intelligence coalition as the anchor of “global Britain”. Duda is the only leader outside that group, a nod of solidarity to Nato’s eastern flank. She is also sending negative signals: a handful of countries have not been invited to the funeral – Russia, Belarus, Venezuela, Syria, Afghanistan and Myanmar. The strength of the snub has been underlined by the fact that North Korea did receive an invite in the post, albeit just at ambassadorial level. The sting was felt in Moscow. The Russian foreign ministry called the snub “deeply immoral” and “blasphemous” to the Queen’s memory. China has been invited, and Beijing is sending Vice-President Wang Qishan, despite the fact that Chinese officials were barred from visiting the Queen’s coffin as it lay in state. The Speaker of the House of Commons refused them entry because China had banned several members of parliament for their criticism of the country’s human rights record. The Saudi Crown Prince, Mohammed bin Salman, is expected to come to London to convey Riyadh’s condolences. However, he is not expected to attend the funeral. It is unclear whether that is due to Buckingham Palace’s fear of negative publicity or his reluctance to take part in an event in which he would not be accorded front-row status albeit with other leaders. If the crown prince does come – a final decision had yet to be made on Saturday – he will hope it will prove a stepping stone away from isolation after the 2018 murder of the dissident and Washington Post columnist Jamal Khashoggi. His human rights record has continued to sink with the recent 45-year prison term imposed on a mother of five for tweets deemed to be critical. He will be hoping to lever his family’s long relationship with King Charles, who visited Saudi Arabia a dozen times as Prince of Wales. Truly international funeral diplomacy is relatively recent. It relies on air travel to fly in leaders from around the world within a few days, and refrigeration to preserve the deceased until they arrive. • The headline of this article was amended on 18 September 2022 to better reflect the content of the story.