The decision was due to deadly floods in the south of France, which both Mr Macron and Prime Minister Edouard Philippe were monitoring, the official said.
The official could not say if the reshuffle would take place before the weekly cabinet meeting on Wednesday.
Mr Macron has recently suffered a number of political blows including the resignations of three ministers since the end of August.
The new cabinet line-up, which had been expected shortly after Gerard Collomb resigned as interior minister on October 2, has been portrayed as imminent for at least a week.
Opposition politicians say the delay shows that Mr Macron’s political party, Republique En Marche, which was created barely two years ago to prepare his bid for the presidency, is struggling to attract candidates to join the government.
After a positive first few months in office, the 40-year-old French President has seen his popularity wane.
Most opinion polls now put his approval rating at barely 30 percent, less than half the level shortly after he took office.
Opponents have been emboldened.
“Postponed again! It’s not a government reshuffle anymore, it’s a collapse: that of the President’s authority,” hard-left leader Jean-Luc Melenchon tweeted.
Mr Macron and his government say he and Philippe are simply taking the time needed to put together the right team.
“In any organisation … you need to take the time to know people, make sure you have the same mindset, check everything,” Macron told France 24 and RFI television on Friday.
“I’m doing things calmly,” he said, adding that the government was carrying on normally with its work.
Philippe has taken on the interior portfolio on an interim basis.