UN aid chief Baroness Amos on Tuesday suggested more intervention in humanitarian emergencies as she said some states were aggressively asserting sovereignty rights to stop action being taken to protect civilians.

Amos cited Syria as an example after the United Nations Security Council had to adopt two resolutions to authorise the delivery of cross-border humanitarian aid in a bid to reach millions of people in need as a result of the country's civil war.

"I don't think that the Syrian government has ever forgiven me. They see me as personally responsible for pushing the Security Council to agree to those resolutions," Amos told the Council of Foreign Relations in New York.

Amos, who will step down in March after more than four years, also said the conflict in Syria has been her low point. More than 12 million people in Syria need help, while another 3.2 million have fled the conflict that has killed some 200,000 people.

"Perhaps we could have pressured the Security Council earlier to get the resolutions that we did," she said.

Amos said there was not enough accountability at the United Nations and that while the Security Council has recognised flagrant violations of international humanitarian law around the world, "there is no action after that".

"As millions of people are forced to flee, as there is abuse on an unprecedented scale of girls and women in many countries ... and action is not being taken in relation to this, I ask the question: should we not be more interventionist?" she said.

But Amos said she did not necessarily mean "boots on the ground" intervention.

"I'm asking the question about an architecture that we already have, a body of rules and law that we already have that we are not holding ourselves accountable to. I see this as a significant failure," she said.