US President George W Bush issued an executive order targeting officials "hindering democratic reform in Zimbabwe", including Mr Mugabe himself.
Mr Bush had already issued sanctions against Mr Mugabe and 76 other officials two years ago, but he US leader says deteriorating conditions in Zimbabwe had forced him to act again.
The White House said suppression of opposition groups, free media and the judiciary had prompted the measures.
In a letter to congressional leaders, President Bush said the opposition and civil society in Zimbabwe remained suppressed.
"Zimbabwe's parliamentary elections in March 2005 were not free or fair," he wrote.
"Recent demolitions of low-income housing and informal markets have caused 700,000 people to lose their homes, jobs or both. Additional measures are required to promote democratic change."
The new additions to the censured list will be banned from business dealings with US citizens.
Under the new order, US treasury secretaries and the state department will now be allowed to add to the list without a presidential order.
"This action is not aimed at the people of Zimbabwe but rather at those most responsible for their plight," said White House spokeswoman Dana Perino.
Reform?
The move comes as Zimbabweans prepare to go to the polls on Saturday to elect members to a new and controversial upper house of parliament.
Critics argue the money being spent on the ballot should be used to alleviate the country’s chronic food shortages and the economic meltdown.
There is little excitement about the elections despite radio and television messages exhorting people to vote for ruling party candidates and news stories about the rift in the main opposition over contesting the polls.
President Robert Mugabe's ZANU PF party, which won a landslide victory in
elections in March, has already used a two-thirds majority in the house to approve constitutional changes in August to re-introduce a bicameral legislature abolished in 1990.
"The question is what benefit will I get if I go to vote and the answer is nothing," said Ella Tayengwa, a 46-year-old mother of four from the populous township of Tafara in Harare.
A widow for six years, she ran a profitable vegetable shop that was razed to the ground during a controversial government blitz on illegal urban structures.
"The senate is not for us but rather for ZANU PF elite so I would rather stay at home on the polling day as my way of protest," she said.
"The majority of us have no food and some who lost their homes are still living in the open so nobody cares about an election that will not make their lives any better."
"A caring government would have used the 90 billion dollars budgeted for the elections to feed its people," Tayengwa added.
International aid agencies estimate that some 4.3 million people out of Zimbabwe's population of 13 million require food assistance.
The country's major labour movement said the senate was a waste of scarce
money as Zimbabwe is in the throes of its worst economic crisis ever.
Zimbabwe's economy has been on a downturn over the past six years
characterised by triple-digit inflation, more than 70 percent unemployment and chronic shortages of basic goods like sugar, cooking oil and fuel.
Critics of the senate said it was a ploy by Mugabe to appease ruling party
members who lost in the March parliamentary elections.
Others say it is aimed at further buttressing the stranglehold Mugabe's party has on the legislature.
The senate has caused a split in the main opposition Movement for Democratic Change (MDC) party after 26 party members defied a call by their leader Morgan Tsvangirai to boycott the polls.
Mr Tsvangirai argued that the senate was a waste of money, especially at a
time of acute economic distress.