GENEVA (AP) _ Negotiators from the United States, China and the two Koreas on Friday wrapped up their latest round of talks aimed at ending almost five decades of cold war on the Korean peninsula.

The four delegations heard reports Friday from the chairmen of two working groups, which during the week have been discussing ways to reduce tensions and put in place a permanent peace.

In a joint statement, the delegations said they had ``useful, productive discussions'' during their four days of talks and would meet again in mid-April.

The process of replacing the armistice that ended the 1950-53 Korean War with a formal peace treaty is expected to take years. The four-party talks started in December 1997 and went through two rounds last year, largely taken up by procedural wrangling.

Delegates have agreed on procedures for the two working groups, which will present proposals to the delegates, officials said Thursday. North Korea has chaired this round in the Swiss city of Geneva.

North Korea has said talks could be affected by the issue of one of its diplomats, who it claims was kidnapped in Berlin last week by South Korean agents and then handed over to the United States.

South Korea says the diplomat and his wife defected and are seeking asylum in the United States.

The United States and North Korea are holding separate talks over U.S. demands for access to a suspected North Korean underground nuclear weapons site. Those talks are to resume this weekend.