@Amol S.
Of course the source of fentanyl is Mexico and the USA itself, as president Trump clearly mentions but he also mentioned Venezuela.
Companies from China ship the neccesary chemicals to produce fentanyl to Mexico and the USA.
He needed an excuse or perhaps some CIA lead pointed towards fentanyl production and shipping from Venezuela. CIA has used such methods before.
And he accuses the governor of Colorado having ties with the drug cartels and the government of Venezuela.
Since they caught 1.7 million fentanyl pills in Colorado.