The German defense minister arrived on Monday in the southeastern Polish town of Zamosc, where some 320 German troops have been stationed since January.

The deployment — near NATO member Poland's border with Ukraine — has previously been a source of diplomatic wrangling between the two countries.

Boris Pistorius in Poland — the agenda 

Pistorius visited the barracks where German forces operate three Patriot missile air defense systems at two separate locations.

He met his Polish counterpart, Mariusz Blaszczak, before visiting the positions outside the city from where the missiles would be fired.

The Patriot system uses surface-to-air missiles manufactured by the US company Raytheon and Lockheed to counter threats from the air.

The US State Department says the Patriot is capable of "bringing down cruise missiles, short-range ballistic missiles, and aircraft at a significantly higher ceiling than previously provided air defense systems."

Tank hub ultimatum?

After meeting Blaszczak, Pistorius pushed for negotiations on the establishment of a maintenance hub in Poland, to repair Leopard tanks damaged in Ukraine, to be finished within the next 10 days.

An agreement on extending the deployment is thought to be being held up by fraught separate negotiations on the maintenance hub.

"Time is of the essence... We believe the talks [on the maintenance hub] should, if at all possible, be completed within the next 10 days so that we know in what direction to plan," Pistorius said.

Both German and Polish companies are involved in the negotiations on the maintenance facility, as well as both countries' governments. It is thought that the main problems are with the corporate rather than the diplomatic side.

Pistorius' remark about a possible change in direction has been seen as a veiled threat to choose a location outside Poland for the maintenance hub.

Germany, Poland and the Patriot missile question

There was a political squabble between Germany and Poland over the deployment of the Patriots on Polish soil, something that Warsaw had requested.

Former German Defense Minister Christine Lambrecht agreed to move the Patriots after a missile strike that hit Polish territory in November.

In a twist that irritated Berlin, Blaszczak suggested that Germany ought to instead station the Patriots in Ukraine.

After a period of tensions between the two governments, Warsaw finally said it would accept them.

After meeting Pistorius, Blaszczak said he hoped that the Patriot systems would not stay in Poland until at least the end of the year. The original deployment had only been envisaged to stay until the end of June. 

Germany is set to move Patriot units from Slovakia, as well as some "supporting elements" from Poland, to Lithuania ahead of a July NATO summit in that country's capital, Vilnius.

rc/ab (dpa, Reuters)