Polish drivers have been blocking roads to three crossings, in what they call a response to government inaction over a loss of business to foreign competitors since Russia's invasion of Ukraine in 2022.
They insist on the return of a limited number of licenses for Ukrainian truckers, a demand Kyiv said it would not consider.
"Negotiations have not yet led to anything, and Polish carriers continue to block three main directions," Ukrainian border guard spokesman Andriy Demchenko said in televised comments.
Demchenko added that 1,300 trucks had been in line from the Polish side at the Yahodyn checkpoint, and 500 trucks at both Krakovets and Rava-Ruska, where the blocking was occurring.
Congestion by about 1,100 trucks was starting at the Shehyni checkpoint because of drives changing their routes, he said.
Another round of negotiations took place on Monday, the Ukrainian deputy infrastructure minister said. Ukraine was trying to find a compromise but the situation was complicated, Deputy Minister Serhiy Derkach said.
"The absurdity of the demands is that the Polish protesters do not appeal to their government, but want Ukraine to apply to the EU for licenses," Derkach said on Facebook.
Protest organiser Tomasz Borkowski blamed a lack of willingness to talk from the Ukrainian side for the lack of progress.
He said that Polish truckers wanted empty trucks from the European Union to be excluded from an electronic queuing system and for permits to be introduced for Polish and Ukrainian companies for the commercial transport of goods.
Derkach said Ukraine had offered to introduce separate lanes for empty trucks at two border crossings. Protesters say such a suggestion would not solve the problem of long waiting times.
(Reporting by Yuliia Dysa in Gdansk, Karol Badohal in Warsaw; additional reporting by Alan Charlish; editing by Angus MacSwan and Jonathan Oatis)
