(Writes through after second day of talks)

By Chris Buckley

BEIJING, Dec 9 (Reuters) - Nuclear disarmament negotiators fell short of agreement on Tuesday on rules about probing North Korea's nuclear activities, with talks in Beijing set to continue with no hints of an impending breakthrough.

North Korea partly disabled its Yongbyon nuclear facility this year in a disarmament-for-aid deal, but the six-party talks have so far failed to agree on a protocol to check the North's declaration of nuclear activities and move disarmament forward.

Progress at the negotiations in Beijing would be a diplomatic trophy for outgoing U.S. President George W. Bush, weeks before he gives way to President-elect Barack Obama.

"If we can get through this it would be an important milestone on that [disarmament] road, but with the understanding there is still a long way to go," chief U.S. envoy Christopher Hill said after a second day of negotiations.

Hill avoided suggesting there was an impending breakthrough over the draft verification rules written by Chinese negotiators.

"The Chinese obviously did a lot of work on it overnight, tried to address everyone's concerns. Obviously, that's not easy to do," Hill told reporters.

"As you know we are very concerned that we have real verification, that when we get to important phases of verification there is no confusion," he said.

Japan's Kyodo news agency quoted Japanese negotiator Akitaka Saiki as saying Japan, the United States, South Korea and Russia all expressed views about the Chinese verification draft.

"China's draft document on a verification protocol has room for improvement," Saiki was quoted as saying.

The talks were to last three days from Monday and Hill joked that reporters should not check out of hotel rooms yet. Analysts believe Pyongyang will tread water, waiting to test Obama's intentions.

"The key issue really is how much control over its nuclear plans North Korea is willing to give away," said Zhang Liangui, an expert on the issue at the Central Party School in Beijing, a top Communist Party think-tank.

"I don't think the United States' bottom line on verification will change under President Obama, so the key is North Korea's bottom line .... North Korea doesn't want to give away an inch on this without making it a hard-won deal."

The talks bring together North and South Korea, China, the United States, Japan and Russia.

Further complicating the talks are sour relations between North and South Korea, and a feud between Pyongyang and Tokyo over the kidnapping of Japanese nationals decades ago. The North has said it will not recognise Japan's role in the talks.

Chinese Foreign Ministry spokesman Liu Jianchao urged the negotiators to exercise "patience and wisdom" as they pore over the potential protocol document drafted by his government.

"China has along with the other parties constantly raised new suggestions and proposals on this issue," he said of the verification standoff.

The most contention has centred on the North's reluctance to allow international inspectors to take nuclear samples out of the country for testing.

Earlier, Saiki warned that serious disputes divided North Korea from the other five parties.

North Korea held its first atomic test explosion in 2006 and the talks, begun in 2003, have made fitful progress since then.

Hill said he was unsure what the North -- officially called the Democratic People's Republic of Korea (DPRK) -- thought of the latest draft verification rules.

"It's a draft that tries to reflect a lot of people's points of view, and I don't know where the DPRK is on that," he said. (Additional reporting by Emma Graham-Harrison in BEIJING and Chisa Fujioka in TOKYO; Editing by Nick Macfie and Paul Tait)

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