Poland and several other countries have said they want to supply Ukraine with German-made Leopard 2 tanks for its defence against Russia but German Chancellor Olaf Scholz has held back so far from sending them or allowing other NATO countries to do so.
Leopard tanks, which are used by an array of NATO countries and require Berlin's approval for re-export, are seen by defence experts as the most suitable for Ukraine.
Poland will ask Germany for permission to re-export Leopard 2 tanks to Ukraine, but even without it Warsaw could send them as part of a coalition of countries, Polish Prime Minister Mateusz Morawiecki said on Monday.
In an apparent shift in Germany's position, Foreign Minister Annalena Baerbock said on Sunday her government would not block Poland if it were to send its Leopard 2 tanks.
The following explains defence export rules in Germany and other countries and the way such deals have been handled previously:
HOW DO GOVERNMENTS CORRECTLY RE-EXPORT GERMAN TANKS?
All German-built weapons of war come with an end use certificate that means their new owner needs Berlin's approval if it wants to pass on that weapon to another country.
Re-export requests usually get the green light if the arms are set to go to other North Atlantic Treaty Organization (NATO) members or closely allied countries.
The approval is withheld under German law "if there is reason to assume that it would run counter to Germany's ambition to entertain good relations to other countries".
The same goes for cases where the weapons may be used to wage a war of aggression or the re-export approval might violate Germany's obligations under international law.
HOW ARE DIPLOMATIC HICCUPS PREVENTED?
As defence exports are a touchy issue in Germany, foreign countries usually do not directly submit a formal request for re-export to the German authorities.
They will rather sound out Berlin's stance by making a so-called "preliminary inquiry", giving Germany the chance to signal whether it is ready to supply the requested weapon or not.
If not, the foreign country abstains from submitting a formal re-export request, and no diplomatic harm is done.
This mechanism means that Poland can, by submitting a formal re-export request, force Scholz to spell out whether he is prepared to see Poland send its Leopards to Ukraine or not.
In the past, though, the German government has been playing for time by not responding to export requests in sensitive cases for a long time.
But an official Polish request would still raise the pressure on Scholz to take a decision.
WHAT ARE THE REPERCUSSIONS IF TANKS ARE SENT WITHOUT APPROVAL?
If tanks were sent without Berlin's consent, a potential consequence could be Germany refusing to supply spare parts for them, said defence analyst Konrad Muzyka.
"That is why it is so important from Warsaw's perspective not to step out of line and create a larger coalition," he said. "Because, of course, the political problem for Germany if they wanted to cut off the supply of spare parts would be much bigger if there was a coalition."
Poland's Morawiecki said: "The condition for us at the moment is to build at least a small coalition of countries."
NO APPROVAL MEANS NO FRESH SPARE PARTS, NO MAINTENANCE
Tanks are high maintenance weapons. They are hulks of steel, but very sensitive ones and will break down quickly without maintenance and a ready supply of spare parts.
Nonetheless, Poland with a large fleet of almost 250 Leopard tanks can rely on extensive stocks of spare parts and a capable defence industry, according to experts, which should enable it to service any Leopards handed over to Ukraine for a certain time.
In the long run, however, Warsaw or Kyiv would still likely have to come back to Germany to purchase more spare parts.
GERMANY'S HIGH HURDLES FOR DEFENCE EXPORTS
Germany has one of the toughest defence export regimes in the world – largely due to its bloody pre-1945 past.
There have been attempts to soften the rules to make cooperation on defence projects with other countries such as France or Britain easier but nothing has been implemented so far, partly due to the opposition of the Greens.
HOW ABOUT SWITZERLAND?
Switzerland has blocked the re-export of Swiss-made weaponry to Ukraine citing the country's long-held tradition of neutrality that is enshrined in international law, but the government is coming under increasing pressure to change its stance.
Germany was rebuffed last year when it asked the Swiss government for permission to send 12,400 rounds of 35mm ammunition for the Gepard anti-aircraft tank that Berlin has supplied to Ukraine. A request to be allowed to send other ammunition was also denied.
Switzerland also blocked a request by Denmark to allow the transfer of Swiss-made Piranha III armoured vehicles.
The government is examining a request from Spain to allow the transfer of two anti-aircraft guns, but said approval is "probably not possible".
The export of the weapons or ammunition to Ukraine is blocked by the so-called non-export declaration, which buyers of Swiss armaments have to sign, as well as a specific embargo on arms sales to Ukraine and Russia.
However, the leader of the centre-right Free Liberals party has brought a motion to scrap the declaration for countries with similar values to Switzerland, a move backed by other politicians.
FRANCE
French defence companies need to submit a request to the ministry of armed forces if they aim to export weapons to countries outside the European Union such as Ukraine.
There are several types of export and transfer licenses, and they may be subject to conditions.
Most of the time, the manufacturer must obtain commitments from its client on the final destination and non-re-export of the materials delivered, which may only be transferred to a third party after prior agreement from the French authorities.
UNITED STATES
The United States maintains strict controls over the transfer of U.S. weapons from allies to third parties.
The so called "third party transfers" require permission from the U.S. government if there is any content on the weapons system that falls under a U.S. government regulation named the International Traffic in Arms Regulations (ITAR).
Outside of third party transfers, there are two major ways foreign governments purchase arms from U.S. companies: direct commercial sales, negotiated between a government and a company; and foreign military sales, in which a foreign government typically contacts a Department of Defense official at the U.S. embassy in their capital. Both require approval by the U.S. government.
(Reporting by Sabine Siebold in Berlin, John Revill in Zurich, Marine Strauss in Brussels and Justyna Pawlak, Alan Charlish and Anna Wlodarczak-Semczuk in Warsaw, Mike Stone in Washington; editing by Grant McCool)
