The publisher confirmed that both titles will miss their respective spring 2011 and winter 2011 dates and will be given new release schedules soon.
In a statement, franchise director Fumito Ueda said that he "sincerely" apologised for the delay of The Last Guardian.
"I announced at last year's Tokyo Game Show that the release timing of The Last Guardian which is currently being developed would be holiday 2011," he said.
"However, to provide more challenging and better quality of content to users and to fulfil First Party Studio's obligations, I decided to postpone its release timing.
"All the members of my production team are working together at a fast pace to develop and release the game in First Party Studio quality."
He added: "I sincerely apologise to all the customers who have been waiting for The Last Guardian for so long, but I beg for your patience. I will also announce the new release timing at a later time."
The Last Guardian was first revealed at TGS in 2009, and was originally expected for release in 2010.
Meanwhile, the long-rumoured ICO / Shadow of the Colossus Collection was officially confirmed at last year's TGS, and will remaster the PS2 adventure titles with 720p visuals, Trophies and support for 3D.
Watch the latest trailer for The Last Guardian below: