President Donald Trump has accused Pakistan of lying and deceiving the United States while receiving billions of dollars in foreign aid.
In his first tweet of the year, he also alleged that Pakistan harboured terrorists sought by US forces.
“They have given us nothing but lies & deceit, thinking of our leaders as fools,” Mr Trump wrote.
The US is considering withholding more than $250m (£185m) in aid that it delayed sending to Islamabad in August.
The move is being considered due to Pakistan’s perceived failure to crack down more effectively on terror groups, The New York Times reports.
In response, the Pakistani foreign ministry has pledged to help international efforts to combat terrorism.
“The United States has foolishly given Pakistan more than 33 billion dollars in aid over the last 15 years”, Mr Trump wrote.
He added: “They give safe haven to the terrorists we hunt in Afghanistan, with little help. No more!”
Pakistan’s Foreign Minister Khawaja Asif acknowledged the tweet, and said his country would respond to “let the world know the truth”.
In August, Mr Asif met with the US ambassador in Islamabad where he said Pakistan had made “immense sacrifices” fighting terrorism but wanted to keep working with the international community “to eliminate the menace of terrorism”.
But Mr Trump has criticised Pakistan for offering a “safe haven” to terrorists in the past.
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In a speech in August, he said: “We have been paying Pakistan billions and billions of dollars at the same time they are housing the very terrorists that we are fighting.”
“It is time for Pakistan to demonstrate its commitment to civilisation, order, and to peace”, he added.
US Secretary of State Rex Tillerson has also put pressure on Pakistan over its perceived backing for the Taliban in Afghanistan.
The US is a key ally to the country, which enjoys a special status as a non-Nato alliance partner and has received billions of dollars in aid.
But Mr Tillerson has said this “could be on the table for discussion if in fact they are unwilling to change their posture or change their approach to how they are dealing with the numerous terrorist organisations that find safe haven in Pakistan.”
Pakistan has already had millions of dollars of US aid withheld for allegedly not taking enough action against the Taliban-allied Haqqani network.