WASHINGTON - The Obama administration insisted on Tuesday it had not offered any sweeteners to North Korea in its nuclear standoff with the West in return for its release of two American journalists to former U.S. President Bill Clinton.

But a senior administration official said, without providing specifics, that Clinton did talk to North Korea's leadership about the positive things that could flow from freeing the two women who had been held by Pyongyang since March.

President Clinton had made clear that this was a purely private humanitarian mission, the official, speaking on condition of anonymity, told reporters, after North Korean leader Kim Jong-il granted the journalists a pardon and allowed them to leave the country with Clinton.

North Korea had requested Clinton's visit and the Obama administration granted its approval only after Pyongyang agreed in advance that the journalists would be freed and there would be no linkage to the nuclear issue, the official said.

Analysts warned that Washington faced a risky task of trying to convince the impoverished state to give up dreams of becoming a nuclear weapons power without being seen to reward it for repeated military provocations or ignoring the demands of others in the region.

The U.S. official said Washington would keep up its efforts to enforce international sanctions imposed on North Korea over its nuclear defiance.

The North Koreans have two paths, the official said,

He warned that continued provocative behavior would lead to further international isolation of Pyongyang but said it also had the choice of returning to suspended six-party talks on its nuclear disarmament.

Washington, keen to avoid any suggestion it was making official overtures to North Korean leader Kim Jong-il after his recent nuclear and missile tests, insisted the meeting was a private one by Clinton and denied North Korea's claim he had brought a message from President Barack Obama.

North Korea last year quit five years of on-and-off negotiations with the United States, China, Japan, Russia and South Korea and has since suggested it will only talk with Washington.

(Reporting by Matt Spetalnick, editing by Chris Wilson)