Portugal and the Czech Republic would not object to playing Thursday's Euro 2012 quarter-final clash at the National Stadium under a closed roof if required by poor weather conditions, a UEFA spokeswoman said.
European football's governing body had said it would seek to keep the roof open for the rest of the tournament after a much-criticised decision to close it ahead of the opening match between co-hosts Poland and Greece due to a thunderstorm.
Polish media and officials complained that humid conditions in the stadium contributed to their team's poor second-half performance.
"In the morning we held a team meeting with both teams and there was a question about closing the roof. Both teams agreed if such a need arises," said UEFA spokeswoman Ewa Prokopiak.
Weather forecasters predict an overcast sky on Thursday night with a chance of thunderstorms.