Taliban, who now control or contest more territory than at any time since 2001, will not attend the talks

(Adds statement after end of talks)

By Andrew MacAskill

KABUL, Jan 18 (Reuters) - Afghanistan, Pakistan, China and the United States sat down to talks on Monday aimed at laying the ground for a negotiated end to almost 15 years of war between U.S.-supported government forces and Taliban insurgents now firmly on the offensive.

Taliban forces have stepped up their campaign in the last year to topple the Kabul government, which has struggled since most foreign troops left at the end of 2014. High-profile suicide attacks and Taliban territorial gains in Helmand province have underlined how far Afghanistan remains from peace.

The Taliban, who now control or contest more territory than at any time since they was ousted by a U.S.-led intervention in 2001, did not attend the talks.

The four nations in a statement after the meeting in Kabul called on "all Taliban groups to enter into early talks with the Afghan government to resolve all differences politically."

The next round of talks will be on Feb. 6 in Islamabad.

The ultimate goal of the diplomatic manoeuvring is to get representatives of the Afghan government and the Taliban into direct negotiations.

The first formal peace talks with the Taliban since the start of the war in 2001 collapsed last year after it was announced its founder, Mullah Mohammad Omar, had been dead for two years, throwing the militant group into disarray. The Taliban remain split on whether to participate in talks.

Afghanistan's Foreign Minister Salahuddin Rabbani said earlier on Monday the public would not accept an open-ended process without results and warned the Taliban not to delay joining talks any further.

A suicide bomber who killed 13 people in eastern Afghanistan and a rocket which landed near the Italian embassy in Kabul on Sunday were a reminder of what is at stake.

"The talks are strategically important for everyone involved, but are unlikely to go anywhere right now," said S. Chandrasekharan, director of the South Asia Analysis Group. "The Taliban are making gains and the army is on the defensive. Until there is a stalemate, the talks are unlikely to succeed."

Although the Afghan army and the Taliban are intensifying fighting on the battlefield, a political settlement is seen as the most likely solution to the conflict.

A statement on a Taliban website on Saturday did not rule out joining talks but rejected U.S. involvement, saying the country was to blame for a war that has killed hundreds of thousands of Afghans.

"On the other hand, they take the first row among peace negotiators," the statement said. (Editing by Nick Macfie)

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