Williams and Garcia in Australia squad
The Perth-born 21-year-old has a Welsh grandfather and was tempted by an international career with Wales after being ignored for Socceroos selection, but was swayed by Verbeek to join the Australian fold last year.
The cagey Dutch coach has yet to cut down a provisional 30-man squad to 23, but let slip the talented youngster will fly to South Africa along with Hull City's Richard Garcia.
After initially saying the players would be in the 23, Verbeek hastily back-pedalled to say they would be among the party of 27 that would fly to South Africa.
"Nothing, because they will be in the 23," Verbeek told reporters when asked whether the players' omission from Australia's World Cup warm-up against New Zealand on Monday would hurt their chances of selection.
"They will be in the 27," he corrected himself.
"The plan is to build them for the upcoming three days and from (May) the 27th, the first day in South Africa, they are 100 percent available in the training session.
"Then they have five days to show me that they will be - they can be - in the final 23."
Williams, who was also eligible to play for India and England with parents born in Bombay and Kent respectively, was rewarded with his Socceroos' debut against Japan in their final World Cup qualifier last year.
Twenty-eight year-old Garcia has enjoyed regular first team action with Hull City as an attacking midfielder and striker, but has been troubled by knee injuries over the last year.
With Verbeek's first-choice team well established, local media speculation over injuries and the handful of remaining berths has reached fever pitch as the players arrived in Melbourne for a training camp this week.
The Dutchman is, nonetheless, expected to employ largely the same group of European-based players that took Australia to a surprise second round appearance at the 2006 World Cup in Germany.