MADRID, March 7 - U.S. Deputy Secretary of State Wendy Sherman said on Monday it may become harder to transport arms to Ukraine in the coming days, Reuters reported.

"It is critical that what we send in is what (Ukraine's President Volodymyr) Zelensky asks for. He knows what his military needs," she said at a briefing in Madrid, as part of a week-long trip to visit Turkey, Spain and North Africa.