When the Brazilian and Argentinean soccer teams practiced at the National Stadium Friday, ahead of their exhibition game the following evening, it appeared as though they were training in a huge, vapor-filled bathhouse.

That was due to thick smog in the Bird's Nest, caused by air pollution in the Chinese capital, where the South American duo will square off in the SuperClasico.

Featuring superstars Lionel Messi of Argentina and Brazil's Neymar, the heavyweight friendly has attracted global media focus, as much over concerns for the health of players worth millions as the sporting action.

Brazilian head coach Dunga said the pollution would be a headache. "Yes, the bad air is one of the toughest challenges we are facing. But it's a fair situation for both teams as we both have to play in smoggy air," he said.

"Because of the pollution and jet lag, a lot of our players just couldn't sleep well. It's hard for them to get acclimatized to the environment here," added the coach, who took over the reins for a second time after this summer's World Cup, replacing Luiz Felipe Scolari.

Heavy haze has been lingering in northern and central China since the beginning of this month, covering Beijing, Tianjin and surrounding areas in Hebei province.

The pollution is forecast to remain at least until Saturday, and on Thursday municipal authorities raised the smog alert to orange, the second-highest level.

Gerardo Martino, who succeeded Alejandro Sabella as head coach of Argentina after the World Cup, echoed the words of Dunga, saying that "it's a big challenge for the players to play in such situation (of air pollution)".

Some Chinese fans even made jokes about the condition of the air ahead of the match.

"I wonder if I could see the faces of Messi and Neymar on TV tomorrow," said a micro-blog user nicknamed WeixinCarlos on Sina Weibo, China's largest micro-blogging platform.

Another micro blogger, Leimingshandian said: "Remind the players not to kick a long pass, otherwise their teammate won't see the ball in the air".

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