The UK government has been asked by Benazir Bhutto's political party to help the investigation into her death.
Ms Bhutto's widower has called for UK support
Ms Bhutto was assassinated in Pakistan on Thursday and the cause of her death is disputed.
Prime Minister Gordon Brown urged President Pervez Musharraf to avoid any "significant delay" in holding elections in a telephone conversation.
They also agreed to consider the suggestion of international support to the murder investigation.
Ms Bhutto's widower, Asif Ali Zardari, said the Pakistan People's Party was asking the United Nations and the British government to conduct an investigation into her killing.
He and their 19-year-old son Bilawal have taken over her party.
Downing Street said Mr Brown and President Musharraf agreed on the need for Pakistan to unite and for all sides to pursue a path of reconciliation and restraint.
A spokeswoman said: "Mr Brown underlined the need to push ahead with the democratic process and to avoid any significant delays to the electoral timetable.
"The prime minister also reinforced the UK's offer of an extension to our already significant counter-terrorism cooperation."
On Saturday, Foreign Secretary David Miliband insisted Britain had no reason to doubt the Pakistani government's account of how she died and offered British help with an inquiry.