Workers on the Maracana stadium in Brazil refused to work on Monday as fears grew that Brazil will not be ready to host the 2013 Confederations Cup.
Construction workers on the Rio de Janeiro stadium - which is being refurbished for use in the 2014 World Cup - downed tools on Monday after growing frustrated over delays in negotiations over wages, meal vouchers, overtime and private health insurance for their families.
They agreed to return to work on Tuesday after talks were scheduled for the end of this week but Nilson Duarte, the president of the Union of Workers in the Industry of Heavy Construction (Sitraicp), said: "On Monday, we set up another meeting for all and there may be a larger strike."
Wagner Antunes Siqueira, a director of the Rio de Janeiro heavy industry workers' union, told Reuters: "It was a warning for the construction companies. We are going to wait for negotiations on Friday. If there is no (agreement), we will hold an assembly to vote on an indefinite strike."
The state government said that it was "confident that there will be an agreement between the parties".
The Maracana is due to host the opening of the Confederations Cup, which begins on June 15. The upgrade works must be completed by May 24 for it to be used in the tournament, while a friendly with England is due to be hosted there on June 2.
Preparations for the World Cup have been severely hampered by strikes, and four of the six stadiums to be used in the Confederations Cup remain unfinished, with FIFA having twice put back its deadlines. FIFA secretary general Jerome Valcke said at the end of last month that April 15 was the final cut-off.
"We cannot go beyond this date," he said. "There cannot be any further delays. All the stadiums must be ready by then."