President Trump and Russian President Vladimir Putin agreed Tuesday in a phone call that Syrians have suffered “far too long” in the country's roughly 6-year-old civil war and agreed to participate in cease-fire negotiations and other humanitarian and de-escalation efforts, according to the White House.

Hundreds of thousands of civilians have been killed in the war in which rebel forces are trying to remove President Bashar Assad, whose regime is backed by the Kremlin.

Trump recently took a hard line on Assad for using chemical weapons on civilians in rebel territory -- and bombed an airstrip from which the civilian attacks were launched.

Putin and Trump also discussed safe, or de-escalation, zones to “achieve lasting peace for humanitarian and many other reasons,” the White House said.

The leaders also continued talks on eradicating Middle East terrorism and discussed North Korea’s escalating efforts to build a nuclear warhead and a missile to launch it.

Trump and Putin discussed meeting on the sidelines of the G-20 summit July 7-8 in Hamburg, Germany, according to Interfax, a Moscow-based independent news agency.

They have yet to meet in person. But Trump, during his presidential campaign, praised Putin’s leadership style.

U.S. intelligence officials have said the Kremlin meddled in the 2016 elections, in which Trump upset Democratic candidate Hillary Clinton. That issue is the focus of an FBI and multiple congressional investigations.