NEW YORK — A Texas man pleaded guilty on Wednesday to plotting to assassinate Saudi Arabia’s ambassador to the United States, agreeing to hire a man he thought was a drug dealer in Mexico last year for $1.5 million to carry out the attack with explosives at a Washington restaurant.

Manssor Arbabsiar, 57, entered the plea to two conspiracy charges and a murder-for-hire count in US District Court in Manhattan, where Judge John F. Keenan repeatedly asked Arbabsiar whether he intended to kill the ambassador. Arbabsiar, a US citizen who holds an Iranian passport, said he did.