The food was sent by Poland’s Solidarity trade union to help Belarusian workers protesting at Alexander Lukashenko's claim to a sixth term as president in an election widely dismissed as rigged.
But the convoy carrying 18 tonnes of aid has been stopped at the Belarusian border, according to Polish officials.
Polish Deputy Foreign Minister Paweł Jabłoński said the foreign ministry in Warsaw was “intervening” with the Belarusian authorities.
He added that the convoy sent by the Solidarity union was not "political”.
Solidarity spokesman Marek Lewandowski said on Thursday that a truck carrying aid was stuck on the Belarusian side after crossing the border at Bobrowniki, eastern Poland.
"The Belarusians are creating multiple formal obstacles,” he added.
Solidarity boss Piotr Duda said earlier this week that Belarusians today needed support in the same way that Poles did 40 years ago.
Poland will this month mark 40 years since the Solidarity trade union and freedom movement was founded.
The rise of Solidarity marked the beginning of the end of communism in Central and Eastern Europe, and precipitated the fall of the Berlin Wall in 1989.