First unveiled in February this year, Canon's new EF 200‐400mm f/4L IS USM Extender l.4x, as well as the EF 500mm f/4L IS II USM and EF 600mm f/4L IS II USM had 2011 release dates - until now.

In a statement shared by Canon USA last week, the availability of the three lenses has "yet to be determined." Canon adds: "Additional information regarding the shipping date of each lens will be made available as soon as possible."

The lenses are expected to play an important part in the 2012 London Olympic Games, which start on 27 July 2012.

The EF 500mm f/4L IS II USM and the EF 600mm f/4L IS II USM, which were supposed to be available from mid 2011, will be, respectively, priced at £8999 and £11,299. The Extender has yet to receive a retail price.

Canon UK has yet to return BJP's request for comment.