SOCHI, Russia (AFP) - Demonstrations are planned in 19 cities worldwide on Wednesday seeking to persuade sponsors of the upcoming Winter Olympics to pull out over the country's anti-gay laws.

The protest action in New York, Paris, Saint Petersburg and elsewhere comes the day after Russian President Vladimir Putin pledged that the Sochi games, which open on Friday, will prove a hospitable event, amid a litany of concerns about its suitability as a venue.

Mr Putin arrived in the Sochi region on Tuesday in typically confident mood, taking top International Olympic Committee (IOC) members to meet leopards being bred in the Sochi region as part of a re-introduction programme.

But analysts have said that Mr Putin has staked his personal reputation on the success of the Games, which have been inextricably linked with his name ever since he spearheaded the successful Russian bid in 2007.

The Games have in particular been shadowed by concerns over the implementation in Sochi of a Russian law against "gay propaganda" to minors, as well as security concerns due to the proximity of the region to the violence-plagued Northern Caucasus.

US telecoms giant AT&T on Tuesday joined a growing international chorus of disapproval at Russia's anti-gay law, as activists ramped up a global campaign for Olympic sponsors to boycott the Sochi games.

"We stand against Russia's anti-LGBT law," said AT&T, the biggest US cellphone and landline operator, in a blog on its corporate website.

Its statement came a day before the planned international demonstrations by LGBT activists targeting big-name Olympic sponsors such as McDonald's, Coca-Cola, Samsung, watchmaker Omega and Visa credit cards.

All Out, an international gay rights group, has announced the protests in 19 cities also including London, Rio de Janeiro and Durban, South Africa.

In a statement on Tuesday, it called on Olympic sponsors "to speak out against Russia's anti-gay laws."

"This is the moment to push sponsors to use their economic power to call for an end to these discriminatory laws," the group said on its website.

Meanwhile, gay Norwegian Health Minister Bent Hoeie said he would attend the Winter Paralympics, also in Sochi, with his husband.

Mr Putin assured had IOC president Thomas Bach that all guests would feel comfortable at the Games.

"I want to assure you that we will do everything so that Sochi is a hospitable home for all the participants, for all the guests," he told Mr Bach as he met members of the IOC in Sochi.

"The main task is to make the Sochi Games a celebration for all sport lovers in the world," he added.

Security at the Winter Games has also been a major focus.

A top US counter-terrorism official said on Tuesday that the biggest security threat facing the games was a possible attack in areas outside of Sochi and its heavily-guarded venues.

Mr Matthew Olsen, director of the National Counter-terrorism Centre, said the primary danger came from extremists with Emarat Kavkaz, or the Caucasus Emirate, which was "probably the most prominent terrorist group in Russia".

US President Barack Obama has been assured that the United States is "taking all appropriate steps regarding the safety of Americans" at the February 7-23 games, the White House said on Tuesday.

During a high-level briefing in the Situation Room, Mr Obama directed his team to continue to work closely with the Russian government "and act on any new information that might affect the security of the Games".

Two Austrian athletes taking part in the Winter Olympics have been threatened with kidnap in an anonymous letter, the country's interior ministry said on Tuesday, with local media citing ski star Marlies Schild and Janine Flock as the targets.

Meanwhile, concerns persisted over the safety of the slopestyle course which has already left two snowboard stars injured as US X Games icon Shaun White labelled the run "intimidating".

Mr Putin earlier took French skiing legend Jean Claude Killy, who has been the IOC's pointman for Sochi, and IOC executive director Gilbert Felli in his own jeep to a nature reserve above the city.

Russia is working to reintroduce the Persian leopard to the nearby mountains as part of measures aimed at showing that the Games will benefit and not hurt the environment.

"The ecological situation has improved many times over," said Mr Putin.

"According to some estimates, it has improved by a factor of four."

"There are questions which always crop up during such huge construction but in general the situation has not worsened but improved."

However, environmentalists scoff at such claims, saying that the Games have irreversibly damaged once virgin environments by the sea and in the mountains.

A Russian court on Monday handed a 15-day jail term to a leading environmental critic of the Games, ostensibly for "swearing" in a public place.

The jailing of Yevgeny Vitishko, a geologist and activist with Environmental Watch on the Northern Caucasus (EWNC), was aimed at sidelining him ahead of the opening ceremony, the group said.