The prime minister was said to have been lined up for the US sports ritual at match between the Washington Nationals and the Arizona Diamondbacks on Wednesday night.
But Mr Sunak has reportedly passed up the chance to take part in the ceremonial first pitch, usually reserved for American celebrities and politicians.
Former Tory chairman Jake Berry told Talk TV: “He bottled it – I bet you he bottled it … Political stunts often go wrong. This is one that would be bound to go wrong.”
Asked against whether he had “bottled it” over the potential to muck up the pitch, Mr Berry said: “I simply don’t know. I would have bottled it – if he has bottled it he’s done the right thing.”
Mr Sunak insisted “I wasn’t actually meant to ever do it” when speaking about the pitch to Westminster reporters on the plane to the US.
The prime minister said a British Armed Forces veteran would instead carry out the duty at the event aimed at marking UK-US friendship day.
Mr Sunak joked: “As you guys know, my sport is more cricket than baseball in any case.”
Stuart Taylor, a former British Army warrant office and chief executive of the Allied Forces Foundation, which supports injured servicemen and women, has been chosen to throw the baseball.
Mr Sunak will raise his concerns about the Biden administration’s green subsidy plan when the pair meet in Washington for talks on Thursday.
Senior members of Mr Sunak’s government have criticised Mr Biden’s Inflation Reduction Act – a massive package of tax breaks and subsidies aimed at boosting green industries in the US – as “protectionist” and distorting.
Asked by reporters whether the Biden administration was being protectionist, Mr Sunak said the recent G7 communique “makes it very clear that G7 countries don’t believe in protectionism as the answer to this challenge and also don’t believe in subsidy races that are zero sum”.
One of the other key issues on the agenda for the US visit will be AI. With the US and EU considering measures to regulate AI, Mr Sunak wants to make sure the UK’s voice is also heard.
Mr Sunak’s adviser has warned that AI could become powerful enough to “kill many humans” in only two years’ time, saying even short-term risks were “pretty scary”.
But Tory technology minister Paul Scully has warned that the “Terminator-style” risks of AI destroying should not be emphasised over the benefits it can bring.