By Karolos Grohmann

BUENOS AIRES (Reuters) - Fears Russia's controversial gay law could affect next year's Sochi Winter Games has reached sponsors despite efforts by the hosts to play down the issue, the International Olympic Committee said on Sunday.

The Russian law, which forbids the dissemination of information on homosexuality to minors, has been seen by critics as discriminatory.

It has overshadowed preparations for the Sochi Olympics - a priority for Russian President Vladimir Putin, who wants it to show the country as a modern state with top-notch infrastructure.

"Lately there has been a lot of discussion and I am pushed by several sponsors about what will happen with this new law in Russia," IOC marketing chief Gerhard Heiberg told Sochi Games chief Dmitry Chernyshenko.

"Especially the American sponsors are afraid what could happen. This could ruin a lot for all of us.

"We are not there to try to change the law in Russia," he said during an official Sochi Games progress presentation to the IOC in the Argentine capital.

"This is an internal Russian decision but what will the consequences be? This is possibly a way where we could get some kind of invitation for people to make demonstrations."

The IOC has said it has received written assurances from the Russian government that the issue would not affect Games participants, including accredited people as well as Olympic spectators.

IOC spokesman Mark Adams said while athletes could not use the Games as a platform to make political statements under rule 50 of its Charter, they could speak out outside Olympic venues.

He said the IOC was assured the Russian law would not affect Games participants.

"How this will work in practice is for Russian authorities to work out," Adams told reporters.

But despite the assurances it is still unclear what repercussions this could have on anyone talking about homosexuality in front of minors during the Games or choosing to express his or her sexual orientation in an Olympic venue.

"All necessary clarification has been provided to the IOC directly by the Russian ministry of justice," Chernyshenko said in response.

NO DISCRIMINATION

"The constitution of the Russian Federation guarantees equality of rights for everybody in the country. It explicitly prohibits any form of discrimination," he told the IOC session.

Critics, however, claim it is one of a string of repressive measures introduced by former KGB spy Putin in the first year of his third presidential term that clamp down on dissent, violate gay rights and restrain non-governmental organisations.

"We make this clear. This law recently passed does not prohibit homosexuality directly or indirectly. It does not contradict elements of the Olympic Charter. It will not stop 2014 proudly upholding the Olympic values," Chernyshenko said.

"The law will have no impact for any guest visitor. Whether athletes or just fans or members of the Olympic family, everybody is welcome to enjoy the fantastic Games."

Chernyshenko said Putin had awarded "the highest Russian order" to a homosexual recently. "This is a greatest example of diversity of our country. It's important to have your (IOC) support in this campaign."

IOC officials also questioned Chernyshenko about what they perceived as a lack of media exposure of the Sochi Olympics as well as concerns over empty seats following Moscow's world athletics championships last month that drew only small crowds.

"To my big surprise on the (Moscow) opening day with the president of the country present, the stadium was a third full despite promises of the organising committee," said IOC member Alex Gilady, also a member of the athletics federation (IAAF) television commission.

"Moscow is of course 12-13 million people, Sochi is (much smaller). Would it be in ice competitions or will they (spectators) get to the mountains in numbers to make TV happy?"

Gilady, a former NBC official, said empty seats would be a turnoff for viewers around the world.

"Why should I be the only idiot watching this?", viewers would ask themselves, Gilady said.

(Reporting by Karolos Grohmann, Editing by Tom Bartlett and Alison Wildey)