"As humanitarians we welcome progress where it means real change… we are seeing signs of momentum, fragile glimmers of hope. Fewer bombs are falling; humanitarian access has opened up in some places," the statement, signed on Friday, reads.
The UN agencies have delivered assistance to over six million people in besieged areas of Syria since the beginning of 2016, according to the document.
The UN officials also expressed hope that the round of peace talks between Damascus and the Syrian opposition, which begins in Geneva on Monday, would prevent the five-year conflict from entering its sixth year.
Syria has been mired in civil war since 2011, with government forces loyal to Syrian President Bashar Assad fighting numerous opposition factions and extremist groups, such as Islamic State, which is banned in several countries, including Russia.
Some 4.8 million people have fled the country since the outbreak of war and a further 4.6 million are in need of urgent humanitarian aid, according to UN estimates.