US President Barack Obama has told the CIA it remains¹ key to protecting the country, days after releasing memos² on its harsh interrogation techniques.

美国总统奥巴马肯定了CIA在保护国家安全方面的关键作用，日前他释放了使用严刑拷问方式的CIA探员。

In a visit to CIA HQ to boost morale³（士气，斗志）, he acknowledged recent "difficult" days but told staff they were needed to fight threats from al-Qaeda（基地组织） and piracy⁴.

Mr Obama has already said CIA staff would not be prosecuted⁶ for the methods, which critics say are torture.

He said he would "vigorously"（有力地） protect the CIA just as it protected the US.

"Don't be discouraged by what's happened in the last few weeks," Mr Obama told a large audience who applauded and cheered when he first appeared before them.

"Don't be discouraged that we have to acknowledge that potentially we've made some mistakes.

"That's how we learn. But the fact that we are willing to acknowledge them and then move forward, that is precisely⁷ why I am proud to be president of the United States and that's why you should be proud to be members of the CIA."

He also spoke⁸ of the public's appreciation⁹ of the work and "sacrifices" CIA staff make, emphasising that success was usually secret but failure often resulted in public blame.

The visit follows comments by a former CIA chief who said the memos would limit its ability to pursue terrorists.

It has been revealed（显示，透漏） that two al-Qaeda suspects were waterboarded 266 times.

Quoting one of the memos, The New York Times said Khalid Sheikh Mohammed, the self-confessed planner of the 9/11 attacks, was subjected to the technique, which simulates drowning, 183 times.

The method was used on another suspect, Abu Zubaydah, at least 83 times.

BBC defence and security correspondent Rob Watson says this contrasts starkly¹⁰ with previous accounts given by US intelligence sources that implied both men told all after only the briefest exposure to the technique.

The new information could hardly have emerged at a more sensitive time for President Obama, our correspondent says.

CIA applauded and cheered at Mr Obama's appearance

CIA 'still exposed'

Though highly critical during his election campaign of the CIA's methods, he adds, since coming to office Mr Obama has been anxious to boost morale at the agency and to draw a line under the controversies¹¹（争议，争论） of its recent past.

The former head of the CIA, Michael Hayden, who ran the agency under President George W Bush, said CIA staff might still be open to congressional probes or civil actions by those subjected to the methods.

"There will be more revelations. There will be more commissions. There will be more investigations," he told Fox News network on Sunday,

"And this to an agency ... that is at war and is on the front lines of defending America."

Gen Hayden added that the release of the memos would make it more difficult to get useful information from suspected terrorists.

"I think that teaching our enemies our outer limits, by taking techniques off the table, we have made it more difficult in a whole host of circumstances I can imagine, more difficult for CIA officers to defend the nation," he said.

He also denied that such methods were ineffective.

"The facts of the case are that the use of these techniques against these terrorists made us safer. It really did work," he said.

Other methods mentioned in the memos include week-long sleep deprivation¹², forced nudity（裸露） and the use of painful positions.

Mr Obama on Thursday said he would not prosecute⁵ under anti-torture laws CIA personnel who relied in good faith on Bush administration legal opinions issued after the 11 September attacks.

But he has been criticised by human rights organisations and UN officials, who say charges are necessary to prevent future abuses and to hold people accountable.