Chelsea head coach Enzo Maresca said it is "almost impossible" to train as temperatures in Philadelphia reached 37 degrees ahead of Wednesday's meeting with Esperance de Tunis.
Training was restricted for the Blues the day before the match at Subaru Park which will determine whether they progress to the last 16 of the Club World Cup, with the length of the session cut short and work restricted to a shaded area of the pitch.
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Maresca's team need to avoid defeat against the Tunisian side or face the embarrassing prospect of falling at the first hurdle of FIFA's revamped tournament.
And with conditions heavily impacting preparations the build-up to their final Group D fixture has been far from ideal.
"It is almost impossible to train or to make a session because of the weather," said Maresca. "Now we are trying just to save energy for the game.
"This morning's session has been very, very, very short. It's not easy in these conditions with these temperatures. We are going to try to do our best."
Maresca has said he will rotate his squad for the game with captain Reece James, who has been suffering with illness, one of the players likely to sit out, whilst defender Levi Colwill has also been unwell.
Nicolas Jackson will serve a one-match ban after his red card for a studs-up tackle during the 3-1 defeat to Brazilian side Flamengo.
Asked about the tournament towards the end of the Premier League season, the Italian said that players would not play if they were feeling fatigued in the US.
Chelsea are on three points after their first two matches, following up a 2-0 victory over Major League Soccer side Los Angeles FC with the defeat by Flamengo.
"I always try to avoid excuses," said Maresca. "I always try to be honest. It's not about excuses, it's about reality.
"It's an excuse when it's not hot and we say that it's hot. That is an excuse. But if hot, it's hot. It's difficult to work with these temperatures but we are here and we trying to do our best and we will try to win.
"Now in terms of the session, it's impossible to do a normal session, otherwise you don't save energy for the game.
"We did the session this morning, it was quite short, we prepared for the game and we will try to do our best to go to the next stage."
PA
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