The White House says President Donald Trump has spoken on the phone with Russian President Vladimir Putin.

The White House says Syria, Iran, North Korea and Ukraine were on the agenda.

Trump and Putin spoke informally several times last week when they attended a summit in Vietnam. They agreed on a number of principles for the future of war-torn Syria.

Trump's phone call with the Russian president on Tuesday comes a day after Putin met with Syrian President Bashar Assad. Putin hosted Assad at a Black Sea resort ahead of a summit later this week with Russia, Turkey and Iran.

The Kremlin said Tuesday that Assad was called to Russia to get him to agree to potential peace initiatives drafted by Russia, Iran and Turkey.