Romania's parliament has voted to impeach President Traian Basescu, as part of a power struggle with the country's prime minister.

A total of 256 lawmakers out of 432 voted on Friday in favor of the move, and he could be permanently ousted from power in a national referendum to be held within 30 days. Crin Antonescu of the ruling Liberal Social Union has been appointed interim president.

The bitter feud between the center-right Basescu and his rival, the center-left Prime Minister Victor Ponta has thrown Romania into its worst crisis since it emerged from communist dictatorship over two decades ago.

The United States has led Western concern that Mr. Ponta's coalition government, which took power in May, has been eroding Romania's freedoms.

U.S. State Department spokeswoman Victoria Nuland in a statement late Friday expressed concern about recent developments in Romania that threaten democratic checks and balances and weaken independent institutions, such as the courts. The statement urged that the process of removing the president be conducted in a fully fair and transparent manner.

Some analysts say the effort to remove President Basescu is illegal. His supporters say the move is an attack on democracy in Romania and they are calling for the prime minister's resignation.

President Basescu was impeached in 2007 but survived the subsequent referendum.

The president has been accused of overstepping his powers and violating the country's constitution.