Some senior Obama officials worry about America’s mounting entanglements. Obama backed Saudi Arabia’s intervention in Yemen’s civil war only reluctantly. The decision followed a debate about whether it was better to oppose the Saudi bombing campaign against Yemen’s Houthi rebels, or to play a potentially moderating role, for instance by aiding target selection to reduce civilian casualties. Obama’s decision to send warships off Yemen’s coast also raised the prospect of a naval confrontation with Iran, which has been supplying the Houthis by sea.

In Ukraine, top officials are divided about whether to send lethal arms to forces battling Moscow-backed insurgents. So far Obama has sent only non-lethal aid, including body armor and night vision goggles, but Kerry and other advocates of providing weapons argue that the president’s caution has only hardened Putin’s resolve.

Much as he did in a 2012 debate over arming Syria’s rebels, Obama has so far vetoed more robust action. But on Wednesday the State Department warned that Russia is increasing its training and supply of the separatists in eastern Ukraine, including providing air defense systems and drones. More Russian troops are stationed on Ukraine’s border than at any time since October 2014, the State Department said.