Vladimir Putin will be allowed safe passage through Bulgarian airspace to attend peace talks with US President Donald Trump in Hungary.
In a rare European "olive branch" to the Russian president, Bulgaria's foreign minister said he should have unhindered travel if it helps achieve a ceasefire in Ukraine.
"When efforts are made to achieve peace, if the condition for this is to hold such a meeting, it is very logical for such a meeting to be mediated in all possible ways," said Georg Georgiev.
He added: "How is it proposed to hold the meeting if one of the participants cannot go to it?"
On Monday, France threatened to block the meeting after Emmanuel Macron's foreign minister suggested that Putin should only be allowed to travel to the European Union (EU) if he accepts an unconditional ceasefire.
Jean-Noël Barrot said: "Vladimir Putin's presence on European Union territory only makes sense if it results in the establishment of an immediate and unconditional ceasefire."
The summit, announced after a phone call between Trump and Putin last week, has caused concern from European capitals.
Hungary is considered by many to be the Kremlin's closest European ally. So far, Putin has not been offered any public assistance from an EU member state to facilitate his arrival in Budapest.
The only route to landlocked Hungary without flying over EU or Ukrainian airspace involves a arduous eight-hour flight over Turkey, the Mediterranean, before entering Montenegro or Albania to reach Budapest via Serbia.
If Bulgaria agrees to open its airspace, it would drastically reduce flight times by providing an entry route through the Black Sea nation.
However, Bulgarian officials have not yet received any request from Moscow to transit over their territory for the meeting, a date for which has not yet been confirmed.