UPDATE 1-South Asia leaders urge joint terrorism fight

(Updates with opening of summit, details)

By Krittivas Mukherjee

COLOMBO, Aug 2 (Reuters) - The leaders of South Asia called for fighting terrorism together as a regional summit overshadowed by worsening ties between India and Pakistan, its biggest members, opened on Saturday.

The leaders of the eight-nation South Asian Association for Regional Cooperation (SAARC) plan to sign four agreements, including one on legal cooperation to combat terrorism at the summit in the Sri Lankan capital.

The two-day summit will also frame a declaration on food security for a region which is home to a fifth of humanity and remains one of the poorest in the world.

But concern about terrorism dominated the summit as speaker after speaker underscored the need to fight terrorism unitedly, alongside securing food and energy security. "The challenges of terrorism must be overcome in order for us to realise the potential of greater regional integration... greater economic integration," Afghan President Hamid Karzai said.

India and Pakistan's prime ministers too called for defending the value of pluralism from terrorism, and said a united fight was needed against violence if the region was to grow.

Nepal, Sri Lanka, Bhutan, the Maldives, and Bangladesh make up the rest of SAARC, formed 23 years ago to boost economic growth -- an agenda held back by old rivalries among members.

SAARC summits have often failed to rise above the squabbles of India and Pakistan, mainly over the disputed Kashmir region, hurting progress on issues central to the bloc.