The 74-year-old Swiss president of world football's governing body, who apologised on Tuesday for the errors made by referees this week, has been a stubborn opponent of technology for years.
He effectively closed the door on further discussions about it three months ago at the annual meeting of football's law-making body, the International Football Association Board (IFAB).
"It is obvious that after the experiences so far at this World Cup it would be a nonsense not to reopen the file on goalline technology," Blatter said at a briefing with selected media on Tuesday.
He was referring specifically to the incident in Sunday's England-Germany match at Bloemfontein when a shot from England midfielder Frank Lampard struck the bar and bounced down well over the line when England, chasing a comeback, were 2-1 down.
He said: "We will look again at technology, goalline technology, at the business meeting of the International Football Association Board in Cardiff, Wales in July.
"The only principle we are going to bring back for discussion is goalline technology. For situations like the Mexico game you don't need technology."
Paul Hawkins, whose Hawk-Eye Innovations company of Winchester, England, developed the system, was keeping an open mind about Blatter's comments.
Hawkins told Reuters: "Mr Blatter has said this before and there have been other changes of mind. All he said is that they will reopen the discussion, they haven't said they will change their minds.
"If they're serious about this then they'll contact us and we'll just wait to find out whether this is just a little statement to defuse the current public pressure.
"I have had my hopes dashed too many times in the past to get too excited, but obviously we think we can help make football a better game."
"I am open-minded for anything that would make us more credible," referee Howard Webb told reporters after a World Cup referees' training session in Pretoria.
"Whatever tools I have I will use to the best of my abilities."
