Turkish President Tayyip Erdogan has said Swedish and Finnish delegations should not bother to come to Turkey.
The incumbent members of Nato said earlier on Monday that they would send diplomats to Turkey to try to overcome the country's objections to their plan to join the military alliance.
But President Erdogan has stated Turkey will not approve their bids to join Nato.
He has labelled Sweden a "hatchery" for terrorist organisations, claiming there are terrorists within parliament.
Turkey accuses Sweden and Finland of sheltering people it says are linked to groups it deems terrorists, namely the Kurdistan Workers Party (PKK) militant group and followers of Fethullah Gulen, whom Ankara accuses of orchestrating the 2016 coup attempt against President Erdogan and his government.
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Azovstal - symbol of Ukrainian resistance
Azovstal steelworks has become a symbol of Ukrainian resistance against Russia's invasion.
Hundreds of fighters have been holed up in the tunnels beneath the massive industrial plant, defending the last Ukrainian stronghold in the besieged city of Mariupol.
The strategically located port city came under massive bombardment from Russian forces early in the invasion.
Taking the city would allow them to complete a land bridge between Crimea and the Donbas region, as well as giving Russia full control of more than 80% of Ukraine's Black Sea coastline.
Ukraine says the Russian bombardment and siege of the city killed tens of thousands of people, with reports of bodies lying in the streets. Moscow denies having targeted civilians.
Pummelled with artillery, rockets and missiles, 90% of the city has been damaged or destroyed, Ukrainian officials say.
Only Azovstal held out.
Its defenders had said they were "buying time" for the rest of Ukraine to battle Russian forces and secure Western arms needed to withstand Russia's assault.
Until 10 days ago, there were also hundreds of civilians sheltering at the steel plant, with food, water and medicine in short supply.
It took about a week to evacuate the women, children and the elderly who had been trapped there for more than a month, in an operation coordinated by the UN and the Red Cross, which concluded on 7 May.
Since then, it's believed only the fighters remain - many having vowed to die fighting rather than surrender.