By Dmitriy Rogovitskiy

MOSCOW (Reuters) - Russian hammer thrower Sergei Litvinov believes the country's athletes will be given a lifeline by the Court of Arbitration for Sport (CAS) to compete at next month's Rio Olympics.

Sport's highest court is set to rule by Thursday on the country's suspension from track and field and Litvinov is confident CAS will overturn the ban in time for the Games.

"From a legal point of view, we have very good chances," the 30-year-old told Reuters ahead of the Aug. 5-22 Olympics.

Litvinov, who won bronze at the 2014 European Championships, would be one of Russia's biggest hopes for a medal in Rio but with three weeks to go he still does not know if he can compete.

The sport's world governing International Association of Athletics Federations (IAAF) banned Russia's track and field athletes last year after a World Anti-Doping Agency report uncovered systematic state-sponsored doping within the country.

The ban was extended last month, ruling Russia's athletes out of the Games, subject to an appeal by the All-Russian Athletics Federation (ARAF) to CAS.

At the end of June, Litvinov wrote a letter to IAAF president Sebastian Coe, asking him to explain the criteria needed for Russian athletes to compete in international events.

"My letter wasn't directly addressed to Coe, but was more to those living in the West," said the athlete, who trains just outside Moscow and is coached by his father Sergei Litvinov, who won gold at the 1988 Olympics in Seoul in the hammer.

"People should understand just how absurd our situation is. I think this letter helped. I got through to people that we need help (from)," he said.

Litvinov does not think the IAAF's actions are "politically motivated" but said it was impossible even for clean athletes to show they are not part of the Russian system.

"There is a big attack taking place on Coe and his organization. They are trying to save their reputation by taking tough actions against Russia," he said.

On July 10, the IAAF's Doping Review Board turned down applications from 67 Russian athletes to compete internationally as "neutrals". Only long jumper Darya Klishina, who is based and tested in the United States, got approval.

"The IAAF's decision on July 10 admitted that no one will be able to defend the reputations of those sportsmen who are clean," he said.

"There is no way we can try to show that we are not part of this system. They don't care how and where the doping tests were taken. The IAAF is always using the same excuse. It's really quite funny."

LAST CHANCE

Russia's last chance is in the hands of CAS, who will rule by Thursday on whether they will be able to compete.

"Being clean in legal terms gives us very good chances of getting a positive verdict," Litvinov said.

"To be honest there are a lot of emotions at the moment and I hope that the CAS lawyers will look into this case from a professional legal point of view and without showing any emotion. This is what everything will depend on," he said.

Litvinov accepted that doping had become a "serious problem" in Russian track and field over the last few years.

"The situation has grown over time. We had athletes before who were ready to talk a lot about doping, like the discus thrower Darya Pishchalnikova," Litvinov said.

Olympic discus silver medalist Pishchalnikova got a 10-year ban in 2013 after failing a drugs test for the second time.

"It was only a matter of time before it (widespread doping) would have been exposed. If it had not been whistleblower Yulia Stepanova, then it would have been someone else. She just pulled the trigger. I don't think she should be blamed," said Litvinov.

Former drug cheat Stepanova's revelations helped expose the massive doping problem in her country and the middle-distance runner left Russia and went into hiding after disclosing the issue. She has since been allowed to compete as an individual.

"We at last need to change our policy toward anti-doping," added Litvinov. "There is not a widespread condemnation of doping in Russia and we tend to protect them (drug cheats) more than we condemn them."

In the 2008-2009 season, the Rostov native competed for Germany. However, he has no regrets about returning to Russia in order to compete for the country of his birth.

"My family are in Russia and my son was born here. Everything that happens is for the better and I never planned to return to the West," added Litvinov, who hopes to win a bronze or silver medal in Rio if he is allowed to compete.

(Reporting by Dmitriy Rogovitskiy; Editing by Ken Ferris)