FRANKFURT/MADRID (Reuters) - Spanish building and infrastructure company ACS (>> ACS Actividades de Construccion y Servicios) is more likely than not to make an offer for toll road operator Abertis (>> Abertis Infraestructuras) and is set to decide the matter within the next three to four weeks, people close to the situation said.

The likelihood of ACS going ahead with a bid, which it would do through its German unit Hochtief (>> Hochtief), is seen as above 50 percent, they added.

An all-cash offer, which would be funded with the help of funds as well as a through a capital increase, is under consideration, they said.

ACS and Hochtief declined to comment.

ACS said last week it was still looking into a potential bid for Abertis (>> Abertis Infraestructuras) though it had yet to make a decision on the issue and submit it to its board.

Italy's Atlantia offered 16.3 billion euros (14.28 billion pounds)in May in cash and equity to buy Abertis and ACS announced shortly after it was considering a counterbid.

(Reporting by Arno Schuetze, Andres Gonzalez and Matthias Inverardi)