Swaziland's ministry of home affairs has reportedly said that the changing of the country's name to the Kingdom of eSwatini "won't happen overnight".
The ministry said this as it reacted to concerns that the renaming of the country would have serious financial implications.
King Mswati III, one of the world's few absolute monarchs, announced last week that his country had changed its name to eSwatini to mark 50 years since independence from British rule.
"I would like to announce that Swaziland will now revert to its original name," Mswati said during independence day celebrations that were held on Thursday.
"African countries on getting independence reverted to their ancient names before they were colonised. So from now on the country will be officially known as the Kingdom of eSwatini."
In reaction, critics of the king, who took the throne in 1986 aged 18, said the move was an example of his authoritarian and wasteful reign in a country that suffers dire poverty, said a report by AFP.
"We see here King Mswati's autocratic style," said Alvit Dlamini, head of the Ngwane National Liberatory Congress, a political party which, like others, is not allowed to run in elections.
"He can't change the name of the country on his own. He was supposed to consult the nation."
Dlamini said that the change would be expensive for Swaziland, where 63 percent of the 1.3-million population live below the national poverty line, according to the World Food Programme.
"This will come with major cost implications, we are a broke country," he said.
But according to SABC, Home Affairs Minister Princess Tsandzile Dlamini maintained that the renaming process would be done "cautiously" to prevent high costs.
"The issue has come at the rightful time, we are 50 years old now. We were called by the name that was used by the British, we are now taking back what belongs to us. We are eSwatini, we are most grateful and happy about that. But talking to letterheads of government to passport to everything it would have to take time so that we finish the stock that we have," she was quoted as saying.