Russian president Vladimir Putin is concerned over delays to preparations for the 2018 World Cup.

There are fears that a backlog of work has been noted at 12 construction sites, but Russia's sports minister Pavel Kolobkov said the delays would not affect the World Cup preparations as a whole.

Putin, who was addressing a meeting of the presidential council for sports on Tuesday, said the delays should be sorted in time to avoid last minute rush.

"Any delays in the preparation for the World Cup are inadmissible. Solving problems is mostly complicated at the final stage and we should pay very special attention to it.

"In the final stage, it may seem that everything is done. But if something hasn't been completed it means that nothing has been done. And if we (allow ourselves to) relax, we'll never bring things to a close."

12 venues in 11 Russian cities will host the 2018 World Cup - Moscow, Saint Petersburg, Sochi, Kazan, Saransk, Kaliningrad, Volgograd, Rostov-on-Don, Nizhny Novgorod, Yekaterinburg and Samara.