The training mission, first announced in August last year, had been due to start this month. One battalion of US soldiers is due to train three Ukrainian National Guard battalions.
A US military official, speaking to Reuters on Friday on condition of anonymity, said the training mission had not yet been finalised, Reuters reported.
Later on Friday, a spokesman for US forces in Europe, confirmed the delay in a statement and said: "The US government would like to see the Minsk agreement fulfilled."
"The training mission is currently on hold but Army Europe is prepared to carry out the mission if and when our government decides to move forward," the statement said.