By Greta Ruffino with AP, AFP

World Cup organizers said Friday they were "monitoring closely" the smoke gripping swaths of the United States ahead of the tournament's weekend final in New Jersey.

"There's been discussion about it, and we have somebody with the National Weather Service that sits in FIFA headquarters there, so we're monitoring closely," Andrew Giuliani, White House World Cup task force executive director, told a briefing.

Officials urged people to stay indoors or wear masks outside as air quality reached unhealthy to hazardous levels, prompting concerns about teams training outdoors.

“These are high-level athletes who are moving a lot of air through their lungs during every practice in every game, and really they shouldn’t be practicing outside if the air quality levels are at hazardous sort of ranges for wildfire-related air pollution,” said Dr. Courtney Howard, an emergency room physician and Global Climate and Health Alliance official.