U.S. President Donald Trump repeatedly urged Ukrainian President Volodymyr Zelenskyy to stop attacks on Russian oil refineries during a September 20 phone call, according to a source familiar with the conversation cited by Axios.

The source said Trump raised the issue several times during the call, with the impact of the strikes on global fuel markets featuring prominently in the discussion.

“The word diesel came up many times during the call,” the source told Axios, adding that the attacks were contributing to higher global diesel prices.

Ukrainian President Volodymyr Zelenskyy said following the call that he and Trump would meet this week on the sidelines of the United Nations General Assembly in New York.

The planned talks come as Washington seeks to move the two sides toward reciprocal measures aimed at reducing hostilities and creating conditions for renewed negotiations.