Actor Ben Stiller speaks out on Syria as US warns of intensifying violence

In over eight years of war, the headlines of suffering and violence in Syria have, at times, faded.

Actor Ben Stiller tried to change that on Wednesday.

The goodwill ambassador for the United Nations High Commissioner for Refugees testified in front of the Senate Foreign Relations Committee about the humanitarian impact of the war and what the U.S. should be doing about it.

It couldn't come at a more critical time. There are rising concerns of intense fighting in the country's northwest province Idlib -- the last rebel stronghold that's in the crosshairs of strongman Bashar al Assad and his backers Russia and Iran, but also a hub of terror groups like al-Qaeda's affiliate.

For those areas liberated from the Islamic State, there are major questions about what comes next as the Trump administration plans to draw down its troop levels and has pulled funding and called for other countries to pay for stabilization projects critical to restoring services and keeping terror groups at bay.

During his testimony, Stiller turned quickly to how watching the refugee crisis galvanized him to act: "I didn’t want to just keep watching. I wanted to do something."

"Eight years into this crisis, we must not look away," he said, praising the work of the U.N. refugee agency, but said it is lacking the resources needed to address the crisis.

"Given severe underfunding, there is nothing easy about making daily difficult choices, like which programs to downsize or which families won’t receive thermal blankets during a cold, harsh winter," he added.

Since the conflict began, the U.S. has provided around $9 billion for humanitarian aid, according to the State Department. But the Trump administration has pulled back -- asking others to pay more, moving to withdraw U.S. troops, and refusing to provide funding to rebuild areas under Assad's control.

In March, the U.N. and European Union hosted a donor conference, securing pledges of up to $7 billion for humanitarian aid for Syria. Of that, $397 million came from the U.S., with State Department Special Envoy Jim Jeffrey announcing the majority will go to countries in the region that host hundreds of thousands of Syrian refugees each.

The deeper U.S. cuts have been to stabilization funding -- the projects like rubble removal, de-mining, and restoration of services like running water that the U.S. has said are necessary to restore life to areas freed of ISIS and prevent the rise of a new terror group. Last August, the U.S. cut over $200 million in stabilization, and in this year's budget proposal, the White House wanted to zero out any more funding.

The U.S. is instead "looking for new sources of stability funds," according to Amb. Jeffrey, after securing $325 million from coalition partners last summer, most of that from Saudi Arabia and the United Arab Emirates. But the needs on the ground are great, and it's unclear where new stabilization funding may come from.

What the U.S. has made clear with allies in Europe and the Middle East is that none of them will provide funding for areas controlled by the Assad regime or its supporters. They're trying to use that as leverage over Russia and Assad to come back to U.N. talks about the country's future, knowing that both parties are desperate not to foot the enormous bill to rebuild.

So far, however, it hasn't worked -- with Russia, Iran, and Turkey engaging in their own talks.

But that peace process is fragile. Turkey backs the rebel groups in Idlib, even those with ties to al Qaeda and other jihadists, and Assad, Russia, and Iran want to take back these last strongholds of opposition -- with airstrikes and bombings flaring up in recent weeks.

The State Department said yesterday the U.S. is "alarmed by the escalation of violence," which continues "to destabilize the region, exacerbate the dire humanitarian situation, and cause dozens of civilian deaths and injuries -- many of them children."

"The violence must end," said spokesperson Morgan Ortagus, accusing Russia and the regime of "blatantly" targeting humanitarian groups like the White Helmets, the volunteer EMS responders who have gained international acclaim for their efforts to rescue Syrians from bombings and airstrikes but have also been allegedly attacked by a smear disinformation campaign by Russia.

The head of the White Helmets was in Washington over the last week, meeting with lawmakers and officials at the White House, State Department, and U.S. Agency for International Development and asking for more support. Despite the larger cuts to Syria, the White Helmets received an additional $5 million in U.S. funding in March.

Raed Saleh told ABC News the appointment of Ambassador Jeffrey last year has given the group confidence and they see the U.S. more engaged now, but when asked about Trump's desire to withdraw the U.S. from Syria, militarily and financially, he said they'll "continue to monitor the other developments."

ABC News's Laura Spitalniak contributed to this report.