Retaliatory air strikes against militants in Iraq have destroyed five weapons depots, but the top US commander for the Middle East has acknowledged there are many similar sites the US has not hit because of potential civilian casualties and political sensitivities with the Iraqi government.
Marine General Frank McKenzie said the US decision to target the Iranian-backed Shiite militia group that killed American and British troops in a rocket attack this week sends a strong message to Iran and its proxies.
But he said that as the threat of continued attacks remains high and tensions with Iran have not gone down, the US is beefing up military assets in the region.
"What should now be obvious to everyone is you're not going to be able to fire those at a US or coalition base, hurt or kill our people, and escape unscathed," Gen McKenzie told Pentagon reporters.
He said the US has been aware of the weapons sites and knows where more are.
But it has exercised "restraint" in bombing them because in some cases the strikes would kill "a lot" of civilians.
He said the US works with the Iraqi military to take out the sites, but at times that does not work.
Kataib Hezbollah, the group the US blames for the Wednesday attack at Camp Taji base that killed two US service members and one Briton and wounded 14 other personnel, has not commented on the strikes, but another Iranian-backed group vowed revenge.
The tit-for-tat strikes potentially signal another cycle of violence between Washington and Tehran that could play out inside Iraq.
They threaten to hamper US negotiations with the Iraqi government to keep American troops in the country.
Iraq's military said three army commandos and two federal police officers were killed in the US strikes, and a Shiite official in the holy city of Karbala said one civilian in an under-construction airport complex was also killed.
Gen McKenzie said that the US had talked with the Iraq military and it knew the US attack was imminent.