US welcomes EU's new foreign policy powers

"As the EU develops a more powerful and unified foreign policy voice in the wake of the Lisbon Treaty, our transatlantic partnership will continue to grow."

She declined to mention Ms Ashton's British nationality in the context of the US and UK's old "special relationship," amid concerns in some European capitals that Washington is increasingly keen to do business with Brussels rather than on a bilateral level.

Her remarks also stand in contrast to fears voiced in the European Parliament last year that the US tried to scupper Lisbon ratification because it does not want to compete with a stronger Europe on the international stage.

Ms Clinton and Ms Ashton indicated that the two powers stand side-by-side on future sanctions on Iran.

"Let me be clear: We will not be waited out and we will not back down. Iran has a very clear choice between continued isolation and living up to its international obligations," Ms Clinton said.

"Six years of dialogue by my predecessor Javier Solana has not brought us to the outcome that we would wish. And so we do have to consider what else needs to be done, and we stand ready to do that," Ms Ashton added.

The pair also agreed that more needs to be done to help people in the Haitian countryside following an initial focus on its earthquake-struck capital, Port-au-Prince.

"The most critical issue on our agenda today was the people of Haiti," Ms Ashton said.

The event was not widely covered in US media. But it saw Ms Clinton praise Ms Ashton's personal qualities and refer to her by her first name in a sign of friendship.

"I am grateful to have such a strong, thoughtful, accomplished partner in the efforts that confront us," she said, adding later that: "Cathy and I are statistics kinds of people."

The EU foreign minister's visit to the US capital follows criticism of her handling of the Haiti crisis in the European Parliament on Tuesday, where French and German MEPs said she should have gone to Port-au-Prince to improve the union's visibility as a donor.

The incoming French EU commissioner, Michel Barnier, on Wednesday attacked Ms Ashton on the same grounds, following a week of French grumbling that the US has taken a leading role in helping the one-time French colony.

Catherine Ashton became the EU's new foreign policy supremo on 1 December, the date of entry into life of the Lisbon accord. But she is currently juggling the creation of a new EU diplomatic corps in Brussels together with her international obligations.

"The whole thing is in statu nascendi. It's a bit chaotic for the time being," an EU diplomat said.