In a tweet, Trump described Saeed as "so-called mastermind" of Mumbai attacks when Washington in 2012 had labeled him specially designated global terrorist and had announced a $10 million bounty for information leading to his arrest and conviction.
"After a ten-year search, the so-called mastermind of the Mumbai terror attacks has been arrested in Pakistan. Great pressure has been exerted over the last two years to find him," he said in the tweet without naming Saeed who was arrested by Pakistani authorities outside Lahore.
Saeed has been detained and freed in the past and New Delhi has still not reacted to Pakistan's latest action. He has been addressing his supporters in public meetings despite his earlier detention in 2017.
He had floated Milli Muslim League to contest the general election and had fielded more than 200 candidates without any electoral success. LeT's humanitarian front Jamat-ud-Dawa (JuD) has been active across Pakistan.
Saeed had organized an anti-India rally in February this year.
Hafiz Saeed's re-arrest came ahead of Pakistan Prime Minister Imran Khan's meeting with Trump. Pakistan has also joined the US, Russia and China in finding out a peace solution in Afghanistan by bringing Taliban on board.
The move has not gone down well in India as it was kept out of the crucial initiative. New Delhi is also opposed to postponement of elections in Afghanistan. Pakistan has also opened up its airspace for traffic from India after blocking it for more than five months in the wake of border tension.
( With inputs from IANS )