JOHANNESBURG — Construction workers have agreed to end a weeklong strike that threatened to derail the completion of already tightly-scheduled projects for the World Cup, union officials and employers said today.

Workers agreed on a pay increase of 12 percent, below the earlier demand of 13 percent, and work at sites across South Africa is to resume on Thursday.

"The strike is over," said Lesiba Seshoka, spokesman for the National Union of Mineworkers. "We got a good offer."

About 70,000 workers began striking July 8, stopping work on stadiums, airports, freeways and Johannesburg's new high-speed rail link — projects that are scheduled to be finished by December. The World Cup football championship is to be held in the summer of 2010.

Negotiations were concluded in the early hours of Wednesday morning and an agreement was supposed to have been signed at noon (1000 GMT).

However, the deal was finally signed around 5 p.m. after negotiators spend hours fine-tuning the wording of the agreement.

Union official Bongi Zwana called the strike "successful" and said that the weeklong loss of wages — the strike was on a 'no work, no pay' basis — would hit members hard, but the difficulties were "outweighed by the gains made with the agreement."

Some workers earn about $300 a month, but informal or casual laborers can take home less than $100. Unions have also cited increases in fuel and food costs that are making it harder for workers to make ends meet.

The agreement included a provision that casual workers, who are the least protected in the industry, would now be eligible for some benefits after 18 months on the job.

The terms of the agreement would also become standard for all unions and contractors in South Africa's civil engineering sector, not just the signatories — a change from the previous system that allowed piecemeal adoption and enforcement of standards.

Industry representative Schalk Ackerman called these provisions "historic."

He said that it would be possible for construction projects to get back on schedule.

The settlement did not include a clause that would prevent workers from striking again before the 2010 World Cup, but officials said they thought it unlikely.

Danny Jordaan, the head of the World Cup organizing committee, welcomed the end of the dispute. "Let the construction restart in earnest," he said in a statement.

The protests drew wide attention.

On Tuesday at Soccer City, a World Cup finals venue near Soweto, several hundred protesting workers marched around the stadium, brandishing sharpened sticks and singing a Xhosa-language lament about how hard they worked, but how little they made. There have been sporadic reports of violence and intimidation during the strike.

South Africa, a regional economic powerhouse, has an unemployment rate of about 25 percent and also has entered a recession for the first time in nearly two decades. The economy has shrunk 6.4 percent, putting pressure on companies, and there have already been hundreds of layoffs.

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Associated Press Writer Celean Jacobson and Nkemeleng Nkosi contributed to this report.