More than 3,900 people have been killed in a war on drugs that Mr Duterte declared when he took office previous year.
Philippine demonstrators have torched a giant paper statue of US President Donald Trump in protest against "American imperialism" on Monday as demonstrations against the US leader entered their fourth day during the 31st ASEAN summit in the Philippine capital Manila.
Mr Trump replied: "We've had a great relationship". It is unclear whether Trump raised the issue of human rights when he saw Duterte.
He met with Indian Prime Minister Narendra Modi and highlighted their two nations' "deeper and more comprehensive" ties, looking to strengthen a relationship that is vital to the USA vision of an Indo-Pacific region that attempts to de-emphasize China's influence.
The United States and the Philippines, a former USA colony, have been strategic allies since World War Two but their relations have been strained by anti-US outbursts from Mr Duterte and his enthusiasm for better ties with Russian Federation and China.
Duterte is often referred to as the Trump of Asia, even though Duterte's election preceded Trump's.
Brennan said Trump's ambiguity on Russia's involvement was "very, very worrisome from a national security standpoint".
Philippine President Rodrigo Duterte (doo-TEHR'-tay) has sanctioned a bloody drug war that features extrajudicial killing.
In Hanoi on Sunday, Trump also pointed to sanctions the USA has imposed on Russian Federation as punishment for election meddling. "We are in a bilateral meeting". "He could also have mentioned that future United States assistance was contingent on the Philippines government, initiating proper investigations into all alleged unlawful killings by police and other armed persons".
To Chhoa-Howard, Trump's position on Duterte actually could have been a boon for the human rights cause.
In April 2017, three months after President Trump took office, he called Duterte saying: "I just wanted to congratulate you because I am hearing of the unbelievable job on the drug problem". Duterte, however, made it clear that he won't welcome any discussion on human rights lest he will tell the United States leader to "lay off".
The opening ceremonies of the Association for Southeast Asian Nations conference began with pageantry, including a group photo of the leaders and the summit's traditional handshake. This backdrop makes the conflicting reports from their most recent meetings all the more confusing.
When the reporters asked Trump whether he would raise human rights at the meeting, Duterte replied with: "Whoa, whoa".