The World Health Organization (WHO) said that the warring parties in Yemen have promised it “unconditional movement” of supplies and medical teams under a U.N. ceasefire that came into effect throughout the war-torn country on Tuesday.

Nineteen trucks pre-loaded with medical supplies in Aden and Sanaa are due to begin moving later in the day to start distribution across Yemen, WHO representative Ahmed Shadoul told a news briefing in Geneva, as peace talks began in Switzerland.

Some 150 metric tonnes of supplies in WHO’s warehouse in Djibouti are expected to be shipped to Sanaa on Dec 21 or 22, he said. From there, ships will take them to other Yemeni ports.

“It depends on access, we will plan more if access is really granted. This is just a test,” he said.