U.S. President Donald Trump has threatened to cut off billions of dollars in aid to Pakistan, accusing Islamabad of being a safe haven for extremists.

In his first tweet of 2018, Trump said on January 1 that the United States had "foolishly" given Pakistan more than $33 billion in aid over the last 15 years, "and they have given us nothing but lies & deceit, thinking of our leaders as fools."

"They give safe haven to the terrorists we hunt in Afghanistan, with little help. No more!" he added.

There's been no official comment yet from Islamabad but Foreign Minister Khawaja Asif tweeted that his government was preparing a response that "will let the world know the truth."

Asif was quoted by Pakistan's Urdu-language Geo Television as saying Trump's tweet was the result of frustration and that Washington should pursue diplomatic not military means to deal with Afghanistan's militants.

"America is frustrated over defeat in Afghanistan. America should take the path of dialogue instead of using military might in Afghanistan," Asif was quoted as saying.

The Afghan ambassador to the United States, Hamdullah Mohib, welcomed Trump's tweet.

"A promising message to Afghans who have suffered at the hands of terrorists based in Pakistan for far too long," Mohib tweeted on January 1.

It was not immediately clear why Trump chose to send the message on Pakistan, but in the past he has accused Islamabad of supporting "agents of chaos" and has demanded that Pakistan act against the Taliban and Haqqani network.

The frequency of suspected U.S. drone attacks near the Pakistani-Afghan border has increased notably since Trump introduced his Afghanistan strategy in August.

After a meeting with Afghan President Ashraf Ghani and Chief Executive Abdullah Abdullah at the presidential palace in Kabul late on December 21, Vice President Mike Pence had sharp words for Islamabad, saying that while Pakistan had much to gain from working with the United States, it also has much to lose by harboring "criminals and terrorists."

"President Trump has put Pakistan on notice," Pence said at the time.