After a week-long delay Tonga's prime minister Hu'akavameiliku Siaosi Sovaleni is scheduled to face a vote of no confidence in parliament on Monday.
The challenge has been brought by MP 'Aisake Eke, who claims to have the numbers to topple government.
No-confidence vote looms in Tonga
It is the second vote of no confidence he has brought against Hu'akavameiliku - the first in September last year was defeated 14 votes to 11.
RNZ Pacific's Tonga correspondent Kalafi Moala said Eke claims this time he has more support.
"Although there are still one or two that are unsure, there seems to be very strong [confidence] that the vote of no confidence will go their way," he said.
"As you know there has been a strained relationship between His Majesty and [Hu'akavameiliku].
"But to me the fact that there are nobles involved it shows you that they feel comfortable that the vote of no confidence is not something that [the King] is against."
In an earlier statement, Hu'akavameiliku questioned the timing of the motion just 11 months before the next election.
He also said the vote-of-no-confidence mechanism is not being used in the manner the framers of the Kingdom's constitution intended.