President Donald Trump said Friday that Iranian military commander Qasem Soleimani -- who was assassinated in a US strike -- should have been killed long before.

In his first substantial comments on the operation, carried out earlier Friday at Baghdad's international airport, Trump tweeted that Soleimani "should have been taken out many years ago!"

Soleimani "has killed or badly wounded thousands of Americans over an extended period of time, and was plotting to kill many more...but got caught!" Trump said.

His only earlier comments on the dramatic news included a tweet featuring a picture of a US flag and another, cryptic tweet stating that "Iran never won a war, but never lost a negotiation!"