Hong Kong has been replaced by Beijing as the venue for a meeting of Apec finance ministers and central bankers later this year.
The surprise move by the central government, described by one Apec official as "rare", led to wild speculation about the reasons for the switch.
Some politicians linked it to a radical political rally planned to take place in the city's main financial district in the summer.
But the organisers dismissed that theory yesterday.
Officials of the Asia Pacific Economic Co-operation forum (Apec) said the decision was made because US President Barack Obama asked for the leaders' meeting to be pushed back from October to November.
Obama needed to be at home for campaigning in the US mid-term elections, said an Apec official, who asked not to be named.
The leaders' summit, including a meeting between Obama and President Xi Jinping , will be the highlight of the event.
"Such a big change is indeed rare and we haven't seen it for years. This reflects that China and the US are working really hard to ensure the meeting [between Xi and Obama] will take place," said the Apec official.
Because of the change, the meeting of finance chiefs originally scheduled for September - and which would have worked out the broad economic issues for the political leaders to ratify later - has been postponed by a couple of weeks as well. The organisers said this would cause logistical problems, such as hotel bookings, and it would be easier to manage the meetings if all the events were held in Beijing.
About 800 people were expected to attend the Hong Kong meetings. David Dodwell, executive director of the Hong Kong-Apec Trade Policy Group, said the idea of a switch had been circulated for about three weeks.
"Clearly this is upsetting because we were looking forward to hosting a meeting that is a natural fit for Hong Kong," Dodwell said.
Discussions are still taking place on whether it will be possible to keep some of the planned business meetings here to discuss issues of international financial stability and market regulation being tackled by the Asia-Pacific Financial Forum.
The explanation did not stop politicians in Hong Kong from linking it to the Occupy Central movement. The protest group is urging people to block traffic in Central unless "genuine universal suffrage" is guaranteed for the 2017 chief executive election.
Executive councillor Cheng Yiu-tong believes the venue switch "could be related" to the movement and said this would affect the city's reputation.
"It is worrying, because you won't know how serious Occupy Central will get … so it could be safer [to hold the Apec meetings in Beijing]," he said.
Democratic Party lawmaker Albert Ho Chun-yan said he was worried the decision could indicate that Beijing was bracing for the worst and may adopt a hardline stance that would be likely to trigger angry protests in the city.
But Secretary for Financial Services and the Treasury Professor Chan Ka-keung said the switch was "purely due to co-ordination and time concerns".
He said "only a small amount" had been spent in preparation, with the HK$63 million fund granted for the event still intact.
Macau's chief executive, Dr Fernando Chui Sai-on, said the city's Apec tourism ministers' meeting had received "no notice of changes" and the preparatory work would go ahead.