Ukraine's strike on an Iranian ship in the Caspian Sea is bad news for anyone hoping to avoid a wider war, raising fears the Ukraine and Iran conflicts could merge into one.

• Ukraine hit a ship in the Caspian Sea, killing an Iranian sailor; Ukraine says it carried weapons for Russia, while Iran says it was just hauling steel.
• Iran has promised to retaliate, and Ukraine has no way to shoot down Iran's ballistic missiles.
• The likely goal is to drag the US directly into fighting Russia by merging the two wars, and to win more American weapons.
• The US is running low on missile interceptors, partly from arming Ukraine and Israel, which is why the Iran fight has stalled.
• Trump is downplaying Russian and Chinese help to Iran, claiming both leaders promised him they won't arm Tehran.

Outlook: Iran is expected to strike back at Ukraine, and pressure is building to pull the US and NATO deeper into a combined war.