NEW YORK (CNN/Money) - Union and management negotiators at SBC Communications met throughout the weekend, with both sides reporting some progress but significant differences on some key issues.

100,000 union workers at SBC began a four day strike protesting contract offers. CNNfn's Allan Chernoff reports. Play video (Real or Windows Media)

The Communications Workers of America, which represents more than about 100,000 SBC employees spread across 13 states, called a four-day strike that began early Friday.

The union said it plans to have members return to work at 12:01 a.m. Tuesday, in order to limit the loss of customers and financial damage to the company. But the union said that it is also preparing an effort to have members of AFL-CIO unions shift their business from SBC to AT&T in 11 states where the companies offer competing service.

Company spokesmen told reporters Friday that the company would withdraw its offer to the union if it is not accepted by Monday night. The company issued a statement early Monday saying that its network maintained its normal level of service in the 13 states through the weekend. It said while severe storms Friday and into the weekend created some outage problems in parts of Ohio, Wisconsin and Michigan, the company had brought in additional resources to fix those problems. It did not say where those resources came from.

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Sticking points in the dispute include the union demand for access to company jobs in growth areas, including Internet data services, installation of Wi-Fi hotspots, voice over the Internet (VOIP) and DSL high-speed Internet access. The company said its package guaranteed a job offer for any employee whose job would be eliminated.

The company is also seeking increases in healthcare copayments, which the company said would average $35 per month for union members. It said the lost wages from the four-day strike would cost members more than union members would pay in those co-payments.

The union said that the company is offering no base wage increase, but instead a one-time lump sum payment equal to 4 percent of pay. The union said that lump-sum payment instead of the union demand for a 3 percent base wage increase equates to a savings to SBC of more than $1 billion over four years.

Shares of SBC (SBC: Research, Estimates), a component of the Dow Jones industrial average, gained 2 cents to $24.33 in trading Friday.