Poland’s Prime Minister Donald Tusk has visited his country’s border with the Russian region of Kaliningrad to inspect progress on the construction of military fortifications along the eastern frontier, calling it “an investment in peace”.

Mr Tusk’s visit on Saturday comes a month before Poland is to take over the rotating presidency of the 27-member European Union.

Polish officials say their priority is to urge Europeans to strengthen defences at a time of Russian aggression and with change coming soon in Washington.

Some European leaders are concerned that the incoming administration of US President-elect Donald Trump might be less committed to Europe’s defence.

Mr Tusk also proposed this week that Poland and the Nordic and Baltic countries carry out joint navy patrols in the strategically important Baltic Sea, after the suspected sabotage of undersea data cables.

Poland’s government and army began building the system dubbed East Shield this year.

It will eventually include approximately 500 miles along the Polish borders with Russia and Belarus, at a time when western officials accuse Russia of waging hybrid attacks against the West that include sabotage, the weaponisation of migration, disinformation and other hostile measures.

“The better the Polish border is guarded, the more difficult it is to access for those with bad intentions,” Mr Tusk said at a news conference near the village of Dabrowka as he stood in front of concrete anti-tank barriers.

Poland has been at the mercy of aggressive neighbours for centuries and has become a leading European voice for security at a time when France and Germany are weakened by internal political problems.

Poland aims to spend 4.7% of its gross domestic product on defence next year, making it one of Nato’s leaders in defence spending.

Mr Tusk’s government estimates that the strategic military project will cost at least 10 billion zlotys (£1.96 billion).

Poland’s borders with Russia, Belarus and Ukraine are the easternmost external borders of both the European Union and Nato.

Mr Tusk said he expected the East Shield to eventually be expanded to protect the small Baltic states of Estonia, Latvia and Lithuania.

“Everything we are doing here, and we will also be doing this on the border with Belarus and Ukraine, is to deter and discourage a potential aggressor, which is why it is truly an investment in peace,” Mr Tusk said.

“We will spend billions of zlotys on this, but right now the whole of Europe is observing these investments and our actions with great satisfaction and will support them if necessary.”

He did not elaborate on his plans for reinforcing the border with Ukraine, a close ally.

Along the frontier, anti-tank barriers known as “hedgehogs” will be integrated with natural barriers like ditches.

Mr Tusk said parts of the project are not visible to the naked eye, but it is nonetheless the largest project of its nature in Europe since the end of the Second World War.

The plans also include the construction of threat reconnaissance and detection systems, forward bases, logistics hubs, warehouses and the deployment of anti-drone systems, the state news agency PAP reported.