Sonjica, who faces Filipino boxer Silvester Lopez in a vacant IBO junior-featherweight title contest in East London on Saturday, was full of confidence ahead of the clash.
"I'm not taking anything away from my opponent, but I want to make it clear that I'm going to be crowned the new IBO junior-featherweight champion," Sonjica said.
Sonjica, however, revealed his opponent was a closed book to him.
"My team and I don't know anything about Lopez, but that shouldn't be a problem at all," he said.
"I have prepared myself very well and I'm confident the title will be mine after the fight.
“This is the time for me to make a name in world boxing. There is no better opportunity to win a world title than this one.”
Lopez tipped the scales at 55.65kg at Friday's weigh-in and it was only at his second visit to the scales -- after he was allowed to go run --that he made the 55.34kg limit.
"I sympathise with Lopez and I also think it’s understandable that he initially struggled to make the weight," said promoter Mzimasi Mnguni.
"We have to take into consideration that Lopez only arrived in South Africa on Wednesday. I expected something like this to happen.
"We are, however, very happy that he finally made the required weight and the fight is on now."
Lopez arrived late in the country on Wednesday after missing a connecting flight from Hong Kong to South Africa.
Sonjica has a professional record of 17 victories (12 KOs) and two losses, while Lopez has 20 wins (15 KOs) and five defeats.
Meanwhile, Mnguni confirmed the undercard clash for the vacant SA junior-bantamweight crown between former title holder Unathi Gqokoma and Zolani Tete had been postponed.
"We have postponed the fight after we were informed that Tete fell ill on Thursday," he said.