Washington: As Pakistan is set to form a new government, the US looks for opportunities to work with it to advance the goals of security and stability in South Asia, the State Department has said.

"As Pakistan's elected leaders form a new government, the US will look for opportunities to work with them to advance our goals of security, stability, and prosperity in South Asia," a US State Department spokesperson said in a statement on Thursday.

Pakistan Tehreek-e-Insaf (PTI) chief Imran Khan is set to become the next Prime Minister of the country, promising a new Pakistan.

Washington will be working closely with Islamabad, given the two countries' relationship in the light of the US strategy for South Asia and the issue of Afghan peace talks, the US spokesperson said.

The official further said the US was "concerned by reports of constraints placed on freedoms of expression, association, and the press leading up to the elections".

As ecstatic PTI supporters celebrated, the outgoing Pakistan Muslim League-Nawaz (PML-N), which had been in power since 2013, rejected the results alleging "outright rigging" and vowing it would use "all political and legal options for redressal of these glaring excesses".