(NewsNation) — The United Nations is working to deliver humanitarian aid to Ukrainians including food, water, medicine, shelter and hygiene products, but it has been a challenge.

In the past month, since Russia first invaded Ukraine, there have only been two successful supply drops to Sumy, one successful drop to Kharkiv and no full supply drops to cities like Kherson and Mariupol.

“We and our partners have still not been able to reach areas where people are in desperate need of support, including Mariupol, Kherson and Chernihiv, despite extensive efforts and ongoing engagement with the parties to the conflict,” said Stephane Dujarric, spokesperson for Secretary-General António Guterres of the U.N., in a briefing on Thursday. “We are continuing our dialogue with both parties to the conflict with the aim of urgently, immediately and consistently negotiating and facilitating the delivery of critical humanitarian assistance to the people who have been hardest-hit by this ongoing war.”

Getting much-needed resources to the easternmost cities that are affected greatly by the Russian invasion requires a few steps. The supplies must be taken to Poland first, where the U.N. has rented spaces in the major Polish cities with large airports. Next, the U.N. hires drivers willing to go over the border to Lviv where they can be distributed further east.

One of the key factors preventing deliveries of humanitarian aid is fighting between Russian and Ukrainian forces along the paths that convoys carrying the aid. Delivery is only possible when forces from both sides agree to not fight on those paths.

Russian forces have been accused of violating these agreements.