The federal government intends to formally join the review proceedings initiated by the Sindh government against the Supreme Court's acquittal of the accused in the murder of US journalist Daniel Pearl.

A spokesman of the Attorney General of Pakistan on Saturday announced that the federal government will also be filing an appropriate application before the Supreme Court to be allowed to join as a party in the proceedings and further seek review and recall of the apex court's Jan 28 judgement.

The announcement said that the federal government will file an application for the constitution of a larger bench to hear the review petitions.

In cooperation with the provincial government, the federal government will continue to take all legal steps to bring the perpetrators of this heinous crime to justice in accordance with the law, the spokesman said.

The family of the slain American journalist has also said they plan to appeal the apex court's decision.

The Pearl family “intends to file a review petition against the illegal and unjust majority decision of the Supreme Court of Pakistan,” said a statement issued by the family’s lawyer, Faisal Siddiqui, on Saturday night.

Earlier this week, the SC acquitted Ahmed Omer Saeed Sheikh, the principal accused in murder of the Wall Street Journal’s bureau chief for South Asia, by extending the benefit of the doubt to him.

Headed by Justice Mushir Alam, a three-judge Supreme Court bench also comprising Justice Sardar Tariq Masood and Justice Yahya Afridi ordered that Sheikh, Fahad Naseem Ahmed, Syed Salman Saqib and Shaikh Muhammad Adil be set free forthwith, if not required to be detained in connection with any other case.

On Friday, the Sindh government lodged a review of the top court's ruling in the case. Speaking to AFP, Sindh Prosecutor General Dr Fiaz Shah said the petition was filed to "seek a review and request the court to recall the order of acquittal".

Meanwhile, the United States has expressed its concern to Pakistan regarding Sheikh's acquittal and has said it is ready to prosecute the British-born militant.

In his first statement on Pakistan as the US state secretary, Antony Blinken said he was "deeply concerned by the Pakistani Supreme Court’s decision to acquit those involved in Pearl’s kidnapping and murder and any proposed action to release them".

“We are also prepared to prosecute Sheikh in the US for his horrific crimes against an American citizen," he said in a statement issued late on Thursday evening. "We are committed to securing justice for Pearl’s family and holding terrorists accountable.”

Blinken termed the verdict as an "affront to terrorism victims everywhere" and said that the US expected Pakistan's authorities to “expeditiously review its legal options to ensure justice is served”.

“The court’s decision is an affront to terrorism victims everywhere, including in Pakistan. The United States recognises past Pakistani actions to hold Omar Sheikh accountable and notes that Sheikh currently remains detained under Pakistani law,” he said.

Later, in a phone call with Foreign Minister Shah Mahmood Qureshi, Blinken called for ensuring accountability for "convicted terrorist" Sheikh and others responsible for Pearl's murder.

During the call, FM Qureshi said he assured his counterpart that Pakistan was fully cognisant of its responsibility regarding all legal options within the ambit of the law. He said he conveyed to Blinken that it was the wish of the Pakistan government that "the family of Daniel Pearl should be given justice" but that it should be "within the limits of the law".

Additional input by Reuters