The United States' government has indicated that it wants to see the international community impose greater sanctions against Zimbabwe, BBC reported.
US Secretary of State Condoleezza Rice said she would be consulting "allies" about sanctions and asset freezes against President Mugabe's government.
She described what is happening to the Zimbabwean people as "unconscionable".
International pressure on Mr Mugabe is growing as Zimbabwe battles economic collapse and a cholera epidemic.
An increasing number of African and Western leaders are urging the Zimbabwean president, who is 84, to step down.
Mr Mugabe has denied being to blame for Zimbabwe's problems, and on Friday told members of his ruling Zanu-PF party that he would "never, never, never surrender".
Both the US and the EU have previously imposed some sanctions, chiefly travel and trade restrictions targeting individuals and organisations linked to the Zimbabwean government.
Ms Rice told AFP news agency that she would be consulting with "our allies, particularly with some of our African allies and with the British" about expanding those sanctions.
"I think it is high time that the international community step up the sanctions on this regime," she said.
Robert Mugabe at the assembly of the African Union 30 June
Robert Mugabe rebuffs international criticism of his government
"I don't know how much longer people can let this go on, claiming that it is somehow an internal matter. It is not," referring to the spread of the cholera epidemic to South Africa.
"What is happening to the Zimbabwean people is unconscionable," she added.
The Bush administration has becoming increasingly frustrated with Mr Mugabe, the BBC's Washington correspondent Andy Gallacher says.
US Assistant Secretary of State for Foreign Affairs Jendayi Frazer said on Sunday Washington had "lost confidence in the power-sharing deal being a success with Mugabe in power. He has lost touch with reality".
The UN Security Council was briefed last week on the situation in Zimbabwe, hearing about the stalled power-sharing agreement between Mr Mugabe and his political rivals as well as the cholera crisis.
The meeting ended without agreement on a motion to censure Mr Mugabe.