The EU and US have voiced concern on Chinese and Russian influence in the Balkans as the region's countries prepare to move closer to Western bloc.

China could replace the EU as a major player in the region, German foreign minister Heiko Maas told the Bundestag in a speech on Wednesday (12 September).

Student or retired? Then this plan is for you.

James Mattis (c): 'The kind of of mischief that Russia has practiced ... it's always beyond the pale' (Photo: defense.gov)

"It's important that we offer these [Western Balkan] countries a European perspective, and a reliable one, because they're otherwise turning to other countries, such as China, which are already ready and don't have the values we have," Maas told MPs.

"That's why it's important for us to remain consistent and reliable," he said.

"Europe can export stability, as we have done with the successive enlargements of our union," European Commission president Jean-Claude Juncker told MEPs in a wide-ranging speech in Strasbourg the same day.

"We must find unity when it comes to the Western Balkans - once and for all ... should we not, our immediate neighbourhood will be shaped by others," he said, without naming which "others" he meant.

The remarks come ahead of Macedonia's referendum on a name deal with Greece on 30 September that could unlock its EU and Nato membership bids.

They also come amid an emerging land-swap deal between Kosovo and Serbia that could clear the way to their EU accession.

EU and Nato leaders have flocked to Skopje in recent days to show support for its pro-European government.

US defence chief James Mattis is also planning to visit, but warned that Russia could try to spoil progress.

"I'm going there to make very clear we stand with the Macedonian people," he told press in Washington on Tuesday.

"I'm concerned about it [Russian meddling]. I think that democracies should be left alone," he added.

"If their ambassador wants to make a statement in the paper, that's one thing, but the kind of of mischief that Russia has practiced from Estonia to the United States, from Ukraine and now to Macedonia, it always is adapted to the specific situation and it's always beyond the pale," he said.

Greece recently expelled Russian diplomats accused of plotting unrest in order to destabilise the Macedonia name accord.

Montenegro, last year, accused Russia of trying to stage a coup to stop its Nato entry, which went ahead anyway.

Russia's ally in Bosnia, Serb leader Miroslav Dodik, is also on the EU watchlist for his destabilising calls for secession by the Serb entity in the Bosnian federation, Republika Srpska, ahead of elections there on 30 October.

But Germany's concerns on Chinese influence are linked to Beijing's heavy investment in infrastructure, energy, real estate, and mergers and acquisitions, rather than dirty tricks.

Chinese investment in Bosnia alone topped $3bn (€2.6bn) in 2016 and 2017.

It was over $1bn in Serbia and counted in the hundreds of millions in Albania and Montenegro, compared to some €1bn/year in EU financial aid and €2bn/yr in corporate investment for the whole region in recent times.

The latest warnings come after French leader Emmanuel Macron named Turkey as another EU regional competitor in April.

Turkey has become the third largest investor in Kosovo after spending €340m to buy an airport and an energy firm.

It has also spent a similar amount in Bosnia on rebuilding mosques and Ottoman-era monuments.

"I don't want a Balkans that turns toward Turkey or Russia," Macron said in April.

"European countries that claim to be the cradles of democracy have failed, European Turks must show their strength to the whole world," Erdogan told a rally in Sarajevo in May.