Cornel Marculescu, FINA's executive director, was speaking in the wake of this week's surprise withdrawal of the Mexican city of Guadalajara as host of the 2017 World Aquatics Championships.

That decision was attributed to a reduction in public spending by the Mexican Government, as the domestic economy has grown more slowly than expected with the collapse in oil prices and other factors taking their toll.

The decline in both oil prices and the value of the rouble has also put the Russian economy under pressure, but Marculescu assured insidethegames that the Kazan 2015 budget had not been subject to any cuts.

"This is the biggest event in Russia this year," he said.

Confirming there was "no doubt whatsoever" that the Championships would take place between July 24 and August 9 as planned, he predicted that Kazan 2015 would be "one of the greatest ever World Championships".

This year's World Aquatics Championships will take place in the Kazan Aquatics Palace, built for the 2013 Summer Universiade ©FINA

On 2017, he said FINA hoped to come up with "something concrete" within the next week or two.

Asked to elaborate on his recent statement that the benefit of organising the World Championships was "much higher than the cost of running the event", Marculescu said the event provided an important economic, social and legacy impact.

In recent times, the benefit had always been "double or triple the investment in the Championships", he said.

One particular point of interest at Kazan will be the debut of mixed relays following a successful introduction to last year's World Short Course Championships in Doha.

The events featured will be the mixed 4x100 metres medley relay and the mixed 4x100m freestyle relay.