Officials in the United States are now speaking openly of the possibility of ending talks over Syria with Russia, and Secretary of State John Kerry is leading the way.
After months of diplomacy between the United States and Russia to try to secure a ceasefire in Syria, the latest truce collapsed last week after just days of calm.
Now, speaking at the Atlantic Council research centre in Washington, John Kerry says the United States has never been closer to cutting off talks with Russia.
"We're on the verge of suspending the discussion because it's irrational in the context of the kind of bombing taking place to be sitting there trying to take things seriously. There's no notion, or indication, of the seriousness of purpose with what is taking place right now. So it's one of those moments where we're going to have to pursue other alternatives for a period of time, barring some clearer indication by the warring parties that they're prepared to consider how to approach this more effectively."
The deepening indications of a possible severing of talks come just a day after Mr Kerry warned Russia to stop the bombing of Aleppo.
In support of the Syrian government, Russia has undertaken a heavy bombardment of the city to help recapture the rebel-held east.
The United States has accused Russia of participating in attacks on civilian targets.
And now, Deputy Secretary of State Antony Blinken says President Barack Obama is considering new options for ending the Syrian war.
"The President has asked all of the agencies to put forward options, some familiar, some new, that we are very actively reviewing. When we are able to work through these in the days ahead, we'll have an opportunity to come back and talk about them in detail, but we're in the process of doing that."
The White House says Mr Obama has spoken by telephone with German chancellor Angela Merkel.
It says both agree Russia and the Syrian government bear what they call a "special responsibility" for stopping the fighting and allowing humanitarian aid in.
Half of the hundreds of thousands of civilians trapped in Aleppo, once the country's largest city, are reportedly children.
But despite the talk, Russia says it will carry on bombing the city's east.
Russian presidential press secretary Dmitry Peskov says the air force will continue its support of the Syrian armed forces.
United Nations Humanitarian Affairs Chief Stephen O'Brien has lashed out at what is happening in Aleppo.
He says it fills him with "raw grief, dismay, intense sadness, frustration and an unquenchable anger."
He is calling for some kind of solution.
"Last week, world leaders came to New York, sat around the very table that we're at, and met in ministerial-level meetings. All with no tangible result. Instead, while the world leaders were meeting, violence actually increased. More civilians and more humanitarians were killed. It is time to place blame. It is time this council stopped tolerating the utter disregard for the most basic provisions of international humanitarian law."
