COP26 president Alok Sharma was unable to confirm China would even be sending a delegation to the gathering in November – although he insisted he was “very, very hopeful” they would.
The agreement of China, as the world’s biggest emitter of greenhouse gases, is seen as crucial if the talks are to succeed in slowing global warming.
However, Beijing has been infuriated by the new defence pact by the UK, US and Australia – widely viewed as a move to counter China’s increasing military assertiveness in the Indo-Pacific.
The foreign ministry in Beijing said it was “extremely irresponsible” after the three allies announced plans to collaborate on developing a fleet of nuclear-powered submarines for the Australian navy.
France has also recalled its ambassadors in the US and Australia for consultations in response after its own submarine deal with Australia was axed as a result.
Mr Sharma, who is flying out to New York with Boris Johnson for the United Nations General Assembly, said he would not expect Mr Xi to say whether he was going to Glasgow until nearer the time.
Pressed on the BBC’s The Andrew Marr Show, he was unable to say for certain that there would even be a Chinese delegation at the talks.
“On the issue of whether Xi Jinping is going to come, that is not yet confirmed. Normally these things come a bit closer to summits. I am very, very hopeful that we will have a delegation from China that is coming.
“President Xi Jinping would come for the world leaders’ conference which is the first two days of COP. But, of course, we want China there as part of the negotiations.
“I do feel that they will come for that. I certainly expect that China will send a negotiating team to Glasgow.”
Mr Sharma, who was recently in Beijing for talks ahead of the summit, acknowledged China would have to be a key part of any agreement.
He told Sky News’s Trevor Phillips on Sunday programme: “There is no doubt that China is going to be part of the key to all of this. They are the biggest emitter in the world.
“They have said to me they want the COP26 to be a success. The ball is in their court. We want them to come forward and make it a success together with the rest of the world.”
Mr Sharma said he was confident the talks would be able to go ahead as planned in Glasgow, despite rising Covid levels in Scotland.
He said a range of safety measures were being put in place, including providing vaccines for accredited delegates who would otherwise be unable to access the jab in their own countries.
“I am confident that we are going to have a physical COP26, we are planning for that,” he told the BBC.
“What’s vitally important is that the people who are coming are safe but also the people of Glasgow are safe. I am confident that we will have a safe event.”
Green MP Caroline Lucas (Brighton Pavilion) said the UK Government was “way off track in terms of meeting our own climate targets”.
On the COP26 aims, she told Sky News’s Trevor Phillips on Sunday programme: “I think he’s [COP26 President Alok Sharma] doing his best, but I think his efforts at international diplomacy are being entirely undermined by government actions at home … the first rule of diplomacy is to walk your talk and yet both on the finance for climate and on the emissions reductions, this government is doing the opposite.”
Asked if a sustainable deal can be struck without China, Ms Lucas said: “I think that’s almost impossible to envisage, no. It is absolutely essential that China is there and that’s why I am deeply concerned about this new so-called Aukus deal because we have just enraged the Chinese even more.
“If COP26, these UN climate talks, are our top diplomatic priority then everything else should be taking second place to that, so I’m deeply worried about relations with China.”
Climate protesters had this week targeted the M25, with traffic stopped on several sections of the motorway on Monday and Wednesday and more than 70 arrested each day.
Home secretary Priti Patel responded by calling the climate change protesters "selfish".
On the M25 protests, Ms Lucas said: “I am saying that in extreme situations it is reasonable to take extreme actions and that is what has driven these protesters to do that.
"Personally I prefer to take action where it is closer to the target of that action, so that might be Downing Street, it might be the Treasury, but I fully understand why protesters have felt driven to do something more dramatic than that because government has been ignoring all of those kinds of actions for many, many years, we face an existential crisis, an emergency and we need to take emergency action now.”