Speaking at an event conducted by the Carnegie Endowment for International Peace, Deputy National Security Adviser Jon Finer said Islamabad's conduct raises questions about the country's intentions.

He said: "Recently, Pakistan has developed increasingly sophisticated missile technology. From long range ballistic missile systems to equipment that would enable the testing of significantly larger rocket motors."

The US official said: "If these trend lines continue, Pakistan will have the capability to strike targets well beyond South Asia, including in the United States, raising real questions about Pakistan's intentions."

He said there is a small number of nations which possess both nuclear weapons and missiles that can hit the US homeland.

"So candidly it's hard for us to see Pakistan's actions as anything other than an emerging threat to the United States," he said.

He questioned Pakistan's motivation behind creating such missiles which have the potential to be acted against the US.

"Unfortunately, it is our sense that Pakistan has failed to take these concerns and frankly, the concerns of others in the international community seriously and continues to advance these capabilities," he said.

The US official said Washington will continue to put pressure on Pakistan over its long-range missile programme.

He made the comments at a time when the US  announced sanctions on four entities in Pakistan which include a state-owned defence agency for its involvement in the nuclear-armed South Asian nation's long-range ballistic missile programme.

The four entities sanctioned include Islamabad-based  National Development Complex (NDC) which is responsible for the development of ballistic missiles, including Shaheen series.

Pakistan's described the US sanctions as 'biased'.

"Pakistan’s strategic capabilities are meant to defend its sovereignty and preserve peace and stability in South Asia. The latest installment of sanctions defies the objective of peace and security by aiming to accentuate military asymmetries," Foreign Office spokesperson Mumtaz Zahra Baloch said in a statement as quoted by Geo News.