"President has been clear that he is focused on peace. We need our partners to be committed to that goal as well. We are pausing and reviewing our aid to ensure that it is contributing to a solution," said the official, speaking on the condition of anonymity.
Zelenskiy's office did not immediately respond to a Reuters request for comment.
The move comes after Trump upended US policy on Ukraine and Russia upon taking office in January, adopting a more conciliatory stance towards Moscow - and after an explosive confrontation with Zelenskiy at the White House on Friday in which Trump criticised him for being insufficiently grateful for the Washington's backing in the war with Russia.
On Monday, Trump again said Zelenskiy should be more appreciative of American support after earlier responding angrily to an Associated Press report quoting Zelenskiy as saying the end of the war is "very, very far away."
"This is the worst statement that could have been made by Zelenskyy, and America will not put up with it for much longer!" Trump wrote on Truth Social, using an alternative spelling of the Ukrainian leader's name.
But Trump also suggested on Monday that a deal to open up Ukraine's minerals to US investment could still be agreed despite his frustration with Kyiv, as European leaders floated proposals for a truce in Russia's war with its neighbour.
The Trump administration views a minerals deal as America's way of earning back some of the tens of billions of dollars it has given to Ukraine in financial and military aid since Russia invaded three years ago.
When asked on Monday if the deal was dead, Trump said at the White House: "No, I don't think so."
Trump described it as a "great deal for us" and said he would give an update on the situation on Tuesday night when he addresses a joint session of Congress.
with PA and AP
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