The World Anti-Doping Agency has been frustrated with trying to work with a Russian law enforcement agency investigating cheating.

Four letters sent to Russia by WADA in recent weeks have gone unanswered, and "it seems our offer has fallen on deaf ears," WADA president Craig Reedie said Wednesday.

WADA officials want to join the Russian Investigative Committee visiting the Moscow testing laboratory that was at the heart of a state-backed doping program. Giving WADA access to samples sealed in storage by Russia is a key point to re-accrediting the national anti-doping agency.

The agency, known as RUSADA, has been suspended since November 2015 when WADA investigators first detailed doping in Russian track and field. Drug testing in Russia has since been overseen by officials sent in by WADA.

A subsequent WADA-appointed probe by Richard McLaren detailed orchestrated doping and cover-ups at the 2014 Sochi Olympics.

Reedie told a conference of anti-doping and sports officials that WADA wants to bring Russia "back in from the cold."

"It is just a pity it is taking so long for Russian authorities to make it happen," the WADA president said.

The WADA roadmap to restoring RUSADA's right to work also requires Russia's sports ministry and national Olympic leaders agreeing that McLaren's findings were accurate. That has proved unacceptable to Russia.

"It is time for this situation to change in the interests of clean athletes, in Russia and beyond," said Reedie, adding that "every Russian sporting victory will be questioned" until the country does what is needed to fully return to international sport.