In Washington for four days of meetings with American politicians and intelligence officials, members a European Parliament delegation said they were disappointed only four members of the US Congress agreed to meet with them before returning to Europe on Friday.

"We regret that no more congressmen or members of this administration and of the former one we had asked to meet have accepted or have been in a position to meet our delegation," Carlos Coelho, chairman of the European group, said at a news conference on Thursday.

Giovanni Claudio Fava, an Italian member of the delegation, said senior State Department officials who met with the group Thursday would neither confirm nor deny the existence of secret CIA prisons for terror suspects in Europe.

"No comment" as a valuable piece of information

The US officials, he said, also remained mum on allegations that some 100 detainees were secretly flown by the CIA through Europe to countries like Syria and Egypt where they could be tortured, a practice known as "extraordinary rendition."

Nonetheless, Fava said the delegation would head back to Europe on Friday on a positive note, as even a "no comment" can be construed as valuable information.

In addition to meetings with members of the US administration, the delegation also has held talks with human rights organizations, lawyers and journalists.

Germany's Cem Özdemir, the deputy chairman of the EU group, said it was clear from the discussions with State Department officials that they did not see eye to eye.

"We agreed we need to fight terrorism, but we did not agree on the means to fight terrorism," Özdemir said. "It is important that US officials understand that we are concerned as representatives of 25 states."

Unclear how many flights transported terror suspects

Last month the EU lawmakers released an interim report that said the CIA operated more than 1,000 clandestine flights through Europe since the Sept. 11, 2001 attacks in the United States. It is unclear, however, whether any of the flights were transporting terror suspects.

"After 9/11 it was very clear who were the good guys and the bad guys," Özdemir told a panel discussion this week. "But today I would not say the same thing anymore. It is still clear who are the bad guys, but unfortunately, it's more and more unclear who are the good guys."

John Bellinger, the State Department's senior legal advisor, has acknowledged that the CIA operated flights over Europe but he has dismissed reports that most of the flights carried detainees.

"Despite a good deal of digging on the part of the press and non-governmental organizations, I don't think anybody has ever suggested that there were more than two or three or four renditions that ever went through Europe," Bellinger said after meeting with the EU parliamentarians. "The suggestion that there have been 1,000 or 100 or even 10, I think there is not any support for any of these allegations."

No new details made public

He refused to elaborate on whether any terror suspects were taken to countries where they could be tortured or whether the CIA ran secret prisons in Europe.

Bellinger also denied reports that Washington was applying pressure on East European countries that allegedly housed secret prisons -- such as Romania and Bosnia-Herzegovina -- not to cooperate with the EU probe.

"The United States government has certainly not pressured other countries or other individuals not to cooperate with this enquiry," he told reporters.