The two heavyweights are among five other bids competing for the high-profile commission, including a joint proposal from Frank Gehry and Rem Koolhaas.
However, it is understood Gehry and Koolhaas’ scheme has become sidelined after it was described as being ‘too grandiose and a little utopian’ by the competition organisers.
Speaking to the Daily Telegraph, Monaco’s prime minister Jean-Paul Proust said: ‘It will have to look as if the extension had always been there.’
The Mediterranean tax haven became the focus of a design competition when the principality’s ruler Prince Albert II invited bids back in 2006.
The Prince called for the world’s playground for the rich and famous to be extended out into the sea, creating a peninsula approximately the size of 20 football pitches.
It is understood that the development plans have been estimated to cost anywhere between 5-10 billion euros (£4-8 billion), and will provide up to 275,000m2 of new housing and tourist facilities.
A winner will be chosen from the five bidders and the result is due to be announced by February next year. It is expected that work will begin by 2011 and will last 10 years.