The Transport Ministry disagrees with City Hall's plan to take over the two extended sections of the skytrain connecting Soi Bearing-Samut Prakan and Mor Chit-Khu Khot.
The plan has been floated by Bangkok Metropolitan Administration as it is in the process of negotiating with the Mass Rapid Transit Authority of Thailand (MRTA), which oversees the planned construction of the two sections.
It proposes the city operate the Soi Bearing-Samut Prakan section, which extends beyond Bangkok.
Transport Minister Air Chief Marshal Prajin Juntong said Wednesday the MRTA would consider allowing City Hall to run only one section. "If the city rejects our offer, the MRTA is ready to operate everything," he said.
The MRTA will wait for City Hall's answer before going ahead with its next move, said MRTA board chairman Gen Yodyuth Boonyatikarn.
ACM Prajin has set July as the deadline for the final round of talks between the MRTA and City Hall.
The extension of the skytrain routes, or the Green Line, is part of the government's plan to link the capital with neighbouring provinces with an electric rail network.
The existing elevated rail routes, which are run by Bangkok Mass Transit System Plc (BTS) under its contract with City Hall, end at Soi Bearing and Mor Chit stations.
According to the MRTA, a new 13km section will link Soi Bearing with Samut Prakan province in the southwest of Bangkok while the other 19km route will connect Mor Chit and Saphan Mai in Bangkok with tambon Khu Khot in Pathum Thani's Lam Luk Ka district, to the north of the capital.
The construction of the Mor Chit-Khu Khot section is expected to start in June this year and will take five years to complete.
Meanwhile, Bangkok Metro Plc (BMCL), the current subway operator, insists the new Purple Line, which connects Bang Yai and Bang Sue, will open on Aug 12 next year.
That is a few months before the earlier opening set for December next year, said BMCL managing director Sombat Kitjalaksana.
The operation of electric trains on this 23-kilometre route is required to go through a trial period to ensure smooth and safe travel for commuters. The testing, which will take about six months, will start in October this year after the BMCL buys the first three trains in September.
"This is an electric train. It's not a bus which can serve passengers immediately after delivery," Mr Sombat said.
MRTA governor Peerayudh Singpatanakul said transport officials are planning to use a single ticketing system for the Purple Line which will allow its passengers to use the ticket for the skytrain together with other types of transport including subways and buses.
This system will help operators save on costs and will lead to cheaper fares for commuters, he said.