The United Nations humanitarian chief on Friday called on the UN Security Council to put "sustained pressure" on the Syrian government and rebel groups to let in desperately needed relief.
Valerie Amos told the council the United Nations had been unable for nearly a year to reach more than 2.5 million civilians trapped in the worsening Syria conflict.
She said on top of well over 100,000 war dead, diseases, including feared new cases of polio, are spreading quickly and many people are dying "silently" from cancer and diabetes because of lack of treatment. Malnutrition is also growing.
"Words, despite their ability to shock cannot really paint a picture of the grim and gruesome reality of Syria today," Amos, the UN chief humanitarian coordinator, told the 15-nation council.
The council, largely divided over the 31-month-old conflict, agreed to a non-binding statement this month calling for unhindered humanitarian access.
But Amos said appeals for local ceasefires have gone unheeded.
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The United Nations had made no "major breakthrough" since the statement in efforts with the Syrian government to get extra visas for aid workers and lift other bureaucratic obstacles.
She told the council that with up to 2,000 armed groups operating in Syria, "clashes amongst these groups are increasingly common and key humanitarian routes have been cut off by fighting."
Kidnappings of aid workers and hijackings of aid trucks are "increasingly common." Some drivers now refuse to join convoys "as they fear for their lives," Amos said.
"Without real and sustained pressure from this council on the government of Syria and opposition groups on the ground, it will be impossible to make progress," Amos said.
She said humanitarian workers now face "a race against time" and called on the council "to exert influence and take the necessary action to stop this brutality and violence."
Among the major powers, Russia has backed President Bashar al-Assad's government while the United States, Britain and France support the opposition.
The Western nations say the council must take tougher action to ensure greater humanitarian access.