Rishi Sunak welcomed Andrzej Duda to Downing Street.
The UK prime minister met the Polish president at lunchtime, between two summits on Ukraine.
Mr Duda has launched what has been dubbed his “diplomatic offensive”, in which he will meet European and NATO leaders to encourage support for Ukraine before US president Joe Biden visits Poland later in February to mark one year since the Russian invasion began.
During Mr Duda's time in the UK, he has spoken with BBC journalist Laura Kuenssberg about the difficulties Poland faces providing assistance to Ukraine.
Sending aircraft to would not be an easy decision to make, Mr Duda said, as the country has fewer than 50 F-16 jets in its air force.
It comes after Ukrainian president Volodymyr Zelensky urged allies to provide aircraft for his country to fight Russia more effectively.
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