The ministers also unveiled a plaque at Riga Central station to mark the site of the future station on the 1435mm-gauge line while an exhibition devoted to the project was also held at the station.

"This is a clear sign of the momentum of one of the major railway projects in the EU," said Mr Rimantas Sinkevičius, Lithuanian minister of transport and communications, adding that standard-gauge "will create new possibilities for market integration, economic development and new mobility solutions for passenger and cargo transportation in the Baltic region."

The new line will link Tallinn with Warsaw via Riga and Kaunas and provide a valuable connection to western Europe. Construction is already underway on the first phase of Rail Baltica 1 from the Poland-Lithuania border to a new intermodal terminal at Kaunas, which is expected to conclude later this year. A €24.4m project to upgrade 13km of standard-gauge track from the Polish border to Mockava has increased speeds on the line to 120km/h for passenger trains and 80km/h for freight traffic. Beyond Kaunas, the next phase of the project will extend 1435mm-gauge tracks east to the marshalling yard at Palemonas.

The mixed-traffic Rail Baltica 2 will extend the line to Riga and the Estonian capital Tallinn, with the existing 1520mm-gauge line from Kaunas to the Lithuanian capital Vilnius being converted to dual-gauge.

Up to 85% of the estimated €3.87bn project could be funded by the European Union through its Connecting Europe Facility (CEF) and the latest agreement follows the founding of a joint venture company, RB Rail, to implement the project, by the ministers of Estonia, Latvia and Lithuania in October 2014. The three countries each hold a 33.3% stake in RB Rail and provided the company with €650,000 in start-up capital.

RB Rail subsequently submitted an application to the European Commission for the first round of funding from CEF in February. The application is currently being evaluated and with Rail Baltica considered a key project in the EU's Ten-T core network, the funding agreement is expected to be signed this autumn.

However, securing private finance for the project has not been ruled out.

"Lithuania supports the intention expressed by the EU Transport coordinators to develop further the trans-European transport network and to look at alternative financing instruments as well as to find additional resources," Sinkevičius says. "Although private financing cannot be the only solution for the implementation of the whole Ten-T, it can be an important part of it."

The 728km line will be designed for operation at up to 240km/h and is expected to reduce Tallinn - Riga journey times to around two hours, while Tallinn - Warsaw will be cut to around six hours. Passenger trains will operate at an average of 170km/h on new-build infrastructure. Construction is expected to begin on the Estonian section of the route by 2017 or 2018 and by 2020 on the Latvian section. The entire line is due to be completed by 2024.