Khan was dismissed Sunday after losing a no-confidence vote, and Sharif elected by Pakistan lawmakers the following day.

"The United States congratulates newly elected Pakistani Prime Minister Shehbaz Sharif and we look forward to continuing our long-standing cooperation with Pakistan's government," US Secretary of State Antony Blinken said in a statement.

"The United States views a strong, prosperous, and democratic Pakistan as essential for the interests of both of our countries."

No prime minister has ever served a full term in Pakistan, but Khan is the first to lose office via a vote of no-confidence -- a defeat he has not taken well.

He tried everything to stay in power after losing his majority in parliament, including dissolving the assembly and calling a fresh election.

But the Supreme Court deemed all his actions illegal and ordered lawmakers to reconvene and vote.

Khan insists he has been the victim of a "regime change" conspiracy involving Washington and his opponents, an accusation the United States has vehemently denied.

The cricket star-turned-politician has vowed to take his fight to the streets in the hope of forcing an early election.

Sharif promised an investigation into Khan's allegations.

"If an iota of evidence is provided against us, I will immediately resign," he told parliament.

He may also rethink Pakistan's global alignment, which drifted away from Washington under Khan and closer to Russia and China -- a vital economic partner.