The Olympic rings hang inside London's St. Pancras train station. London will host the Summer Games in 2012. ((Alastair Grant/Associated Press))

Turkish Prime Minister Recep Tayyip Erdogan formally announced Istanbul's bid to host the 2020 Olympics on Saturday and expressed confidence that the city would be successful in its fifth attempt to stage the games.

Erdogan said Turkey's relative economic success and lessons learnt from the previous failed bids made the city a strong contender.

"We are excited because this time we sincerely believe that we will attain our goal," Erdogan said in a nationwide televised speech. The world in the past year was shaken by a heavy economic crisis.

"We successfully emerged from the global crisis. Turkey is one of the fastest growing economies … We have invested in sports and will continue to do so."

Istanbul unsuccessfully bid for the games in 2000, 2004, 2008 and 2012. Erdogan said since its first bid, Turkey had built state of the art stadiums and sports centres in Istanbul and had taken steps to alleviate Istanbul's traffic congestion problem — the city's major problem.

"We had several deficiencies but Istanbul is now a city that has overcome them," Erdogan said, citing new light rail networks and other infrastructure in the city.

Istanbul joins Rome, Madrid and Tokyo who have already announced bids. Another potential candidate is Doha, Qatar.

South Africa announced it would not bid, but has indicated it could still reverse its decision. Dubai, in the United Arab Emirates, which has been hit by the global economic crisis, decided not to bid but has said it would consider bidding in 2024.

The IOC will select the 2020 host city in 2013.

Turkey is trying to raise the country's profile through sports.

Last month, Turkey hosted the European Youth Olympic Festival in the Black Sea port city of Trabzon, an event organized to showcase the country's ability to host major international sporting events.

Other major international sports events held in Turkey recently include the Winter Universiade in the eastern city of Erzurum earlier this year and the 2010 FIBA World Basketball Championships, where the host took the silver medal.

Istanbul has hosted a Formula One Grand Prix since 2005, although it has been dropped from the 2012 calendar.

Turkey will also stage the Mediterranean games in 2013, after neighbouring Greece, suffering a steep economic crisis, decided not to host them.