The European Union and the United Nations on Tuesday appealed for swift political talks to end the long war in Syria, saying the latest territorial gains by Damascus and its allies had not brought peace any closer.
Syrian President Bashar al-Assad, backed by Moscow and Tehran, is pushing a military offensive to wipe out the last few rebel enclaves near Damascus.
Efforts for a negotiated end to the war, that killed half a million people over seven years and displaced millions, are stuck.
"We're seeing in last few weeks, days ... that military gains, territorial gains and military escalation do not bring a political solution, has not brought any change. On the contrary," the UN special envoy for Syria, Staffan de Mistura, told a news conference in Brussels.
He spoke as governments and aid groups gathered in Brussels to pledge more than $6 billion in aid for Syria.
De Mistura's co-host and the EU's top diplomat, Federica Mogherini, said "real, meaningful political negotiations ... are clearly the only way forward."
The proxy war pits Damascus, Russia and Iran against rebels seeking to oust Assad and their backers in Turkey and the West. Islamic militants have also spread havoc in the conflict, where the UN says over 400,000 people are still trapped in sieges.
A British deputy development minister at the Brussels meeting said it was an important signal as the Syrian army continued to use sieges and bombardments to force rebels out.
"We want to make sure that medical facilities stop getting targeted, medical aid stops getting stolen, that gender-based violence is reduced, that the medieval tactics of starvation come to an end," Alistair Burt told Reuters.
The donors would offer new money for humanitarian assistance inside Syria, as well as for the Syrian refugees in Iraq, Jordan, Lebanon and Turkey.
But the United States and the EU - the world's largest donors - refuse to chip in billions of dollars that would eventually be needed to rebuild Syria for as long as Assad does not let the opposition share power.
"We see absolutely no motivation to give up one of the most significant levers that we have in the absence of even minimal movement towards a better political shaping or framework for Syria to make it more, rather than less, stable and secure," said a senior US administration official.