Thailand’s top two mobile operators, AIS and dtac, have signed a 3G network sharing agreement that will initially see them sharing 300 towers but expanding that to 2,000 by the end of the year.

The sharing arrangement, which will be limited to 3G towers operating on the 2.1GHz band, is between AIS subsidiary Advanced Wireless Network and dtac subsidiary TriNet, the Bangkok Post reported.

The announcement comes just days after dtac signed a separate deal with state-owed CAT Telecom to set up two joint ventures to share network assets via separate tower and fibre units. Tower JV Co and Fibre JV Co, both 51:49 ventures, are expected to be established this year and start operations in 2016.

The AIS unit has 22,000 3G base stations and 16,000 towers, while dtac has 15,000 3G base stations and several thousand towers, according to the Post.

Representatives from both operators said the move was just the first step in a long-term partnership, indicating they would work together on future network developments, presumably 4G once they secure licences, to reduce costs by sharing infrastructure.

Number 2 dtac also has a three-year tower leasing deal with True’s tower unit — True Telecommunications Growth Infrastructure Fund (TRUEGIF). Dtac rents several hundred towers from TRUEGIF to boost its coverage.