After years of working to call international attention to the death and destruction caused by Saudi Arabia's U.S.-backed war in Yemen, human rights and anti-war groups expressed cautious optimism that the war-torn, impoverished country may see some relief in the coming weeks, following calls for a ceasefire by the Trump administration.

Secretary of State Mike Pompeo and Defense Secretary James Mattis on Tuesday both called for all participants in the war to come together for peace talks within the next 30 days, putting a stop to a conflict in which Saudi Arabia and the United Arab Emirates (UAE)—with weapons, fuel, and tactical support from countries including the U.S. and U.K.—have killed 16,000 Yemeni civilians and displaced an estimated two million while leaving 22 million on the brink of famine.

The first potential sign of a real shift in US- Saudi relations post #JamalKhashoggi's murder... Mattis calls for ceasefire in Yemen within 30 days https://t.co/HPuNcSCuyz via @CBSPolitics — Trita Parsi (@tparsi) October 31, 2018

Breaking! Yemen war: US presses Saudi Arabia to agree ceasefire. Your pressure is working. We must keep it up! #YemenCantWait https://t.co/XfFhd06rBn — Win Without War (@WinWithoutWar) October 31, 2018

The calls from Mattis and Pompeo come nearly a month after Washington Post journalist Jamal Khashoggi was killed by Saudi agents after expressing criticism of his native country's government. Khashoggi's murder drew international outrage and widespread demands that the Trump administration end its support of the Saudis, including its $110 billion weapons deal with the kingdom.

The International Rescue Committee (IRC), which currently has 800 humanitarian workers in Yemen combating the famine and health crises that have taken hold there since the war began in 2015, called Pompeo and Mattis's remarks "the most significant breakthrough" in the effort to stop the violence.

"It is a very welcome recognition that current policy is failing and needs urgently to be changed to focus on a diplomatic solution," said David Miliband, president of the IRC. "The people of Yemen are now suffering the world's worst humanitarian crisis and the country threatens to become a tinderbox for the region. It is vital that this call for a ceasefire is followed through, and the call for support for the political process heeded."

While Mattis and Pompeo did not speak about specific actions that must be taken in Yemen to immediately lessen suffering, calling only for a "cessation of hostilities" from both the Houthis and the Saudi-led coalition, IRC highlighted the dire circumstances in which Yemenis are living and Miliband demanded a number of immediate steps to ensure that Yemenis are able to access humanitarian aid, food, and medicine.

When we talk about a humanitarian catastrophe, this is what we mean: -22 million people in need of aid to survive. -15 million with no access to clean water. -2 million kids out of school. -millions who don’t know where their next meal will come from. This is Yemen today. pic.twitter.com/GY29XwWaXx — ICRC (@ICRC) October 30, 2018

"All sea ports need to be fully open, Sanaa airport must be opened to humanitarian and commercial traffic, and vital civil servant salary payments must resume to reverse the economic collapse," said Miliband.

Journalist Samuel Oakford of Airwars also called Pompeo's remarks indicative of a major shift—but pointed out that the Secretary of State was careful not to suggest that the Saudis, with the help of the U.S., bear responsibility for Yemenis' suffering.

Pompeo's Yemen statement tonight is one of the most significant since US support began in 2015. It's also carefully worded, w/ Houthis stopping cross border attacks, and only then Coalition stops bombing populated areas. Question is why now? Why wait until so many are starving? pic.twitter.com/ZESLRzlgzv — Samuel Oakford (@samueloakford) October 31, 2018

While Democratic lawmakers including Sens. Chris Murphy (D-Conn.) and Bernie Sanders (I-Vt.) and Rep. Ro Khanna (D-Calif.) have demanded for years that the U.S. government end its backing of the war, the announcement by Mattis and Pompeo notably arrived just after the right-wing Charles Koch Institute made a public call to stop the conflict.

"Given divergent strategic interests and very different values, the United States has long needed to modify our relationship with Saudi Arabia. Riyadh's callous prosecution of a war in Yemen that undermines our interests and the heinous murder of Khashoggi both underscore this," said William Ruger, vice president of research and policy for the Institute, announcing its support for Khanna's resolution to end military aid to the Saudis, which is expected to come to a vote on the House floor next month.

Khanna expressed appreciation for the Institute's statement, but stressed that it is up to Congress to ensure that the U.S. follows through on Pompeo and Mattis's demands for a ceasefire.