Why is Poland stopping sending weapons to Ukraine - and what is the dispute over?

Poland has said it will stop sending weapons to Ukraine amid an ongoing row over grain exports.

In a TV address on Wednesday, Polish Prime Minister Mateusz Morawiecki said: "We are no longer transferring any weapons to Ukraine because we will now arm ourselves with the most modern weapons."

Ukraine's neighbour has been one of its strongest allies, providing tanks, fighter jets and taking in roughly a million refugees.

But tensions over grain could play into Russia's hands if the issues aren't resolved, experts warn.

Here Sky News takes a closer look at what's behind the dispute.

Grain dispute escalates

The origins of current tensions stretch back to the very beginning of the war - and Russia's blockade of Ukrainian grain exports via the Black Sea.

Shipping lanes were blocked, but a deal was struck with Moscow to allow grain to be transported over land.

Although a positive development, it meant neighbouring European countries were flooded with Ukrainian grain, which pushed down prices and left local farmers out of pocket.

To stop this from happening, the European Union temporarily banned Ukrainian grain imports in five countries - Poland, Slovakia, Romania, Bulgaria and Hungary.

The ban expired on 15 September and EU leaders chose not to renew it, but Poland, Slovakia and Hungary decided to continue with it of their own accord.

EU leaders warned it isn't up to individual member states to decide on trade policy within the bloc - and Ukraine filed lawsuits to the World Trade Organization (WTO) over those countries that upheld the ban.

During his visit to the United Nations in New York on Tuesday, President Volodymyr Zelenskyy accused "some in Europe" of "playing out solidarity in a political theatre" and "turning grain into a thriller".

He warned that by doing so, those three nations are "helping set the stage for a Moscow actor".

Poland then summoned its Ukrainian ambassador, before Mr Morawiecki announced the temporary weapons ban and threatened to "add additional products" to the ban too.

He did say, however, that weapons would still be allowed to pass through and be stored in Poland, and that it would honour deals on weapons it had already agreed to.

Zelenskyy comments a 'step too far'

With the Ukrainian economy decimated by the war effort, it is desperate to sell as much of its grain as it can.

But given the level of support it's given, Poland's request that that should not come at the expense of its farmers is "quite reasonable", according to military analyst Sean Bell.

"Ukraine is trying to dump a lot of its grain onto its European neighbours," he tells Sky News. "And Poland, quite reasonably, is saying that's a step too far."

But instead of showing understanding, Mr Zelenskyy's constant efforts to maintain Western support have left him frustrated, Bell says.

He is having to contend with a "growing sentiment" in the West that "Russia is no longer the threat it once was", Bell adds, which has disincentivised countries to give up their own resources to help Ukraine - when there are more pertinent issues at home.

"The problem is President Zelenskyy is clearly tired, he's frustrated, he's angry. And so some of his words haven't been as considered as they have been in the past.

"That has been taken to heart by Poland, who are saying: 'Hang on a minute - look at what we've done for you.'"

Pressure from far-right extends to Slovakia

Many analysts have pointed to upcoming elections in Poland on 15 October as another factor in its defiant stance.

Although Mr Morawiecki's Law and Justice (PiS) party is most likely to win, according to recent polls, its margin over its far-right opponents has tightened.

The Polish far-right has long been critical of the supply of weapons to Ukraine, which has so far cost Poland around a third of its military resources.

So Mr Morawiecki's threats on weapons could be a last-ditch attempt to re-win votes, particularly among farmers.

Ruslan Tradis, a resident fellow for security research at the Atlantic Council's Digital Forensic Research Lab, has pointed out this is a risky game - that could play into Russia's hands.

"The Polish government's far-right policies benefit Russia in the long term," he said. "Recent unfortunate statements from Warsaw show how easily the Kremlin can gain an advantage as long as it uses fears, as happened with the Ukrainian grain topic that became a centre of local politics."

The far-right influence is more of an issue in Slovakia, which has also taken upon itself to uphold the Ukrainian grain ban.

Their elections on 30 September are a closer call than in Poland, Bell says.

They are also less of a support to Ukraine, which means they have less to lose by breaking EU policy over grain.

'Slice of humble pie' from Zelenskyy would resolve dispute

According to Bell, Mr Zelenskyy could easily reverse Poland's position by extending an olive branch.

"There will be a conversation between Zelenskyy and the Polish leadership whereby he'll turn around and say he's very, very grateful for all the help they've provided," he says.

"He'll say his comments weren't aimed at Poland - more at making sure the West upholds its support. It'll be a case of humble pie and clarification of words."

In that case, Poland would be likely to accept the apology, he adds.

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"If Ukraine was to fall, Poland would be next, so I'm confident that this issue will be resolved."

Poland also has a vested interest in continuing other types of support. Its refurbishment of tanks are a good source of revenue and the refugees it has taken in help with its workforce, Bell says.

But he warns that the situation is less clear in Slovakia, where the "dust will need to settle" on the election - before their position can become clear.