"The most important leg of the Middle Corridor Project [to unite Europe and Asia via Anatolia] is fulfilled with the first service of the Baku-Tbilisi-Kars railway," Erdogan said during an inauguration ceremony in Baku along with Azerbaijan's President Ilham Aliyev and Georgian Prime Minister Giorgi Kvirikashvili.
The 826-kilometer (513-mile) railway project connecting Baku with Turkey's northeastern Kars province via Tbilisi was launched in 2007 and construction began in 2008.
Erdogan said the project was "priceless" since it was "laboriously and devotedly" carried out. "So, we declare the establishment of continuous railway link from London to China," he added.
The Turkish leader said the railway would serve a million passengers a year and had 6.5 million tons of freight capacity.
Erdogan said this capacity would rise to three million passengers and 17 million tons of freight by 2034.
"Of course, this will substantially reduce the cost of freight," he added.
Erdogan said the railway's contribution to the region would not just be economic: "The project will politically bring peace, security and stability and, socially, it will bring welfare."
Ilham Aliyev said the railway project was the result of the "brotherhood" of the three countries involved.
He said some believed it was "impossible" for the project to be realized "but, the three countries showed and proved that it is possible".
"Baku-Tbilisi-Kars is a historic, global project. This project will make [our] countries closer," he said.
Kvirikashvili said the project was a bridge between Asia and Europe. “This line will both tie economies and people together,” he added.
European Union welcomed the project, describing it as a “major step” to link the EU, Turkey, Georgia, Azerbaijan, and Central Asia.
Christian Berger, the head of the EU Delegation to Turkey, expressed the EU’s support for projects aiming connectivity with the candidate countries.
“The European Union welcomes the new rail corridor which, coupled with investments, improved infrastructure and logistics coordination will provide better connectivity, new business opportunities and increased trade,” Berger said, adding: “This is at the heart of its Eastern Partnership as well as of its Central Asia strategy.”
Later in the day, Erdogan attended an official dinner hosted by Aliyev.