WASHINGTON (Reuters) - The United States is encouraged that Egypt's interim government has "laid out a plan for the path forward", a US official said on Tuesday when asked about the government's intention to hold parliamentary elections in about six months.

But Washington wants to respond with some caution to the plan for quick elections, unveiled a day after 55 people were killed when troops fired on a crowd supporting Egypt's ousted president Mohamed Mursi, said the official, who spoke on condition of anonymity.

The caution appears to reflect a US desire not to be seen as supporting one side or another in the political crisis in Egypt, where the army last week toppled the president, the country's first freely elected leader and a former member of the Muslim Brotherhood.

The worst day of violence in more than a year has left Egypt, the Arab world's most populous nation, more divided than ever in its modern history, and added pressure on the military-led authorities to explain how they will restore democracy.

While the US has sought to cast itself as not taking sides, its failure to condemn Mr Mursi's ouster or to demand his reinstatement has left many Egyptians with the belief that it is quietly siding with the military and liberal opponents of the Muslim Brotherhood.