Vladimir Putin has opened a bridge between the Russian mainland and Crimea, tightening Russia’s hold over the contested peninsula, which Moscow annexed from Ukraine in 2014.

The 12-mile (19km), $3.7bn (£2.7bn) bridge is Moscow’s only direct road link to Crimea. Russia expects it will carry millions of cars and rail travellers and millions of tons of cargo each year. Previously, all car traffic passed over the Kerch strait by ferry or by passing through Ukraine.

Relations between Russia and Ukraine remain extremely fraught as a simmering conflict continues between Kiev and Moscow-backed separatists in Ukraine’s south-east. In 2016 the US imposed sanctions on Russian companies that were helping to build the bridge across the Kerch strait. Ukraine has said the construction of the bridge shows blatant disregard for international law.

On Tuesday Putin drove an orange Kamaz truck across the bridge as he opened the road to car traffic. “In different historical epochs, even under the tsar priests, people dreamed of building this bridge,” Putin told workers at the ceremony. “Then they returned to this [idea] in the 1930s, the 40s, the 50s. And finally, thanks to your work and your talent, the miracle has happened.”

Russian state media touted the bridge as the “construction of the century”. The Soviet Union and Nazi Germany had considered and then scrapped plans to build a bridge over the Kerch strait. Ferry traffic is often halted because of bad weather.

Facebook Twitter Pinterest Putin sits in a dump truck before driving it on the newly opened bridge. Photograph: Alexei Druzhinin/ Sputnik /Kremlin pool/EPA

Construction was led by Stroygazmontazh, whose owner, Arkady Rotenberg, has close connections to the Kremlin. Rotenberg was Putin’s judo sparring partner. He was hit with sanctions by the US for his proximity to Putin and by the EU for being among those accused of undermining Ukraine’s territorial integrity.

The bridge was completed six months ahead of schedule, according to Russian state news agencies. “I’ve got goosebumps,” Rotenberg told the Russia-24 channel during a live, nationwide broadcast from the bridge.

The bridge can reportedly carry up to 40,000 cars per day, its span is greater than that of the Vasco da Gama bridge in Portugal, previously the longest in Europe.