Cable duo Comcast (CMCSA) and Time Warner Cable (TWC) could arrive at a WiMax deal as early as this weekend, according to people close to the discussions.

In the proposed deal, the cable companies would chip in some $1.5 billion toward a nationwide wireless network construction project led through a joint venture between Sprint (S) and Clearwire (CLWR). Comcast and Time Warner Cable entry into the discussions was first reported Wednesday by The Wall Street Journal.

“There’s a 40% chance of it happening over the weekend,” says a source familiar with the deal.

Comcast was unavailable for comment and Time Warner Cable had no comment.

According to the plan, the cable companies would be teaming with Intel (INTC) and possibly Google (GOOG) in this new venture to build a fast wireless network using WiMax technology. Intel has already signaled its interest and could be in for around $1 billion.

The sources also say a large retailer, presumably Best Buy (BBY), is also interested in the partnership. Best Buy declined to comment.

Among the possible snags to the cable deal is the push by Sprint and Clearwire to get the satellite TV players EchoStar (DISH) and DirecTV (DTV) involved in the deal. Both satellite players are restricted from entering deal talks until late next week as part of an anti-collusion silence period related to the recent wireless auction.

As one source described it, Clearwire and Sprint are running an airwave auction of their own, and they want to make sure they have the most bidders possible. Sprint and Clearwire would contribute their spectrum licenses and infrastructure to the venture, but they still need several billion dollars to make it happen.

Wireless, particularly mobile broadband, is seen as a huge opportunity for the cable companies and the satellite players to add more services and deliver more products to compete with phone companies.

WiMax was in danger of becoming the path not taken on the wireless upgrade map. AT&T (T) and Verizon (VZ) have selected a fast mobile data technology called long term evolution or LTE as the evolution route for their networks. LTE is an extension of Europe’s GSM wireless standard.