Samantha Power said this week she would seek to combat what she called the "crackdown on civil society" in countries including Venezuela.

She was speaking at a US Senate confirmation hearing on Wednesday.

The remarks prompted an angry response from Venezuela's President Nicolas Maduro.

"The Bolivarian Republic of Venezuela hereby ends the process... of finally normalising our diplomatic relations," said Venezuela's foreign ministry in a statement.

It objected to Ms Power's "interventionist agenda", noting that her "disrespectful opinions" were later endorsed by the state department, "contradicting in tone and in content" earlier statements by Secretary of State John Kerry.

Relations between the US and Venezuela have been strained in recent years. They last had ambassadors in each other's capitals in 2010.

Washington angered Caracas by backing the Venezuelan opposition's demand for a full recount of the presidential election in April to replace Hugo Chavez, who died in March.

Mr Chavez's anointed successor, Nicolas Maduro, won the vote by less than two percentage points.

In June, the two countries had tentatively agreed to work towards improving their strained relations, after Venezuela freed and deported a US filmmaker who had been held on conspiracy charges.

During a regional summit in Guatemala, Mr Kerry said he had agreed with Foreign Minister Elias Jaua on an "ongoing, continuing dialogue" in order to "establish a more constructive and positive relationship".

He said the US wanted to "begin to change the dialogue between our countries and hopefully quickly move the appointments of ambassadors between our nations".

Mr Jaua said at the time that for Venezuela it was important to build a relationship based on the principles of mutual respect and no interference in internal affairs.