United Nations: The UN’s humanitarian chief sharply criticised the Syrian government’s lack of progress in allowing desperately needed aid to people in Syria, telling the Security Council on Friday that the regime’s delays in withholding cross-border aid deliveries are “arbitrary and unjustified” - and against international law.

Valerie Amos gave her first such report since the council last month approved a resolution demanding both the government and the opposition allow immediate access everywhere in the war-ravaged country to deliver aid.

Council members said they will in the coming days and weeks discuss the “further steps” that the resolution threatens if its requirements are not met. That will be difficult, as key Syria ally Russia insisted that a reference to sanctions be dropped from the resolution. Russia has blocked three previous resolutions that would have pressured President Bashar Al Assad to end the conflict.

Samantha Power, the US ambassador to the UN, called the briefing by Amos “harrowing” and said the Syrian government has “utterly failed to comply” with the resolution.

While Syria’s ambassador said much has been “achieved” in the month since the resolution, current council president Sylvie Lucas, the Luxembourg ambassador, said, “On the contrary, the situation has only continued to worsen.”

The conflict in Syria is now in its fourth year, with no end in sight. Amos said the violence has “intensified over the past four weeks.” The United Nations months ago stopped issuing death tolls.

UN Secretary-General Ban Ki-moon has said 3.5 million people are estimated to need aid in hard-to-reach areas in Syria, an increase of 1 million since the beginning of the year. Overall, more than 9.3 million people in Syria are in need of humanitarian aid, including 6.5 million internally displaced, Ban said.

The Security Council resolution demands that all parties, especially the Syrian government, promptly allow safe access for humanitarian aid across conflict lines and borders, and it calls on both sides to immediately lift sieges of populated areas. It also demands that all parties stop depriving civilians of food, halt attacks against civilians and demands that all foreign fighters withdraw from Syria.

Amos said the “piecemeal approach” to delivering aid is not enough, and she said the situation will continue to be bleak without “full and unhindered access” to the people in need. Spending days and weeks on approving a single convoy is “a waste of valuable time,” she said.

“The rules of international humanitarian law are also clear,” Amos said. “The continued withholding of consent to cross-border or cross-line relief operations, particularly of commodities privileged throughout the Geneva Conventions — like food, water, medical treatment and supplies, or shelter — is arbitrary and unjustified.”

Her prepared comments to reporters after the closed briefing did not single out the Syrian government by name, but council members did. “Clear responsibility lies with the regime,” said Britain’s ambassador, Mark Lyall Grant.

Grant pointed out that about 220,000 people remain under siege, and Amos said just 6 percent of them have received aid in the past month.

International rights and aid groups lined up Friday to express alarm at the aid crisis, with Human Rights Watch urging the Security Council to “impose punitive measures” against the Syrian government, such as an arms embargo and a referral of the situation to the International Criminal Court.

The Syrian government recently approved the opening of one border crossing with Turkey, but council members appealed for more open crossings along that border, which they said would allow aid to reach an estimated 3.35 million people.

Power blamed the Syrian government alone for denying the U.N. access to the other crossings, which are held by rebels.

UN agencies generally do not cross borders without government permission, even if a government isn’t in control of a certain area or crossing.

On another subject that has alarmed many in the international community, Amos also called the Syrian government’s use of barrel bombs “a flagrant violation of international law.”

Syria’s ambassador, Bashar Ja’afari, denied the use of the bombs, saying, “No. What you see on TV is publicity. ... We are not killing our own people.”