A canal project aimed at alleviating pressure on the busy Bosphorus Strait was launched by Turkish President Tayyip Erdogan on Saturday.

Construction workers poured cement into the foundations of the 1.6 km bridge as a crowd waved Turkish flags.

"We view Kanal Istanbul as a project to save Istanbul's future," Erdogan said during a ceremony.  "We are opening a new page in the history of Turkey's development."

According to Erdogan, the canal would take six years to complete.

The government says it is increasingly dangerous for tankers to make their way between the Black Sea and the Sea of Marmara down the busy Bosphorus, which divides the European and Asian halves of Istanbul.

Already 43,000 ships pass through every year, far more than the 25,000 the government considers safe, causing longer and longer waiting times. By 2050, it is estimated that number will rise to 78,000. The Bosporus has also suffered a series of accidents and collisions in recent months.

The $15 billion project intends to achieve decongestion by laying the foundations of a bridge over the planned route.

Erdogan also argues that the project will create jobs and raise revenue.

The project has, however, faced opposition with critics questioning the viability of a waterway running 45 km (28 miles) through marshland and farms on the western edge of Istanbul, adding that it will damage the environment.

Senior bankers who spoke to Reuters in April said that some of Turkey's biggest banks were hesitant to finance the project due to environmental concerns and the investment risks.

Russia is also concerned that the canal might not be covered by the 1936 Montreux Convention, which restricts the passage of non-Black Sea states' warships through the Bosphorus.

(With input from Reuters)