South and North Korea are trying hard to settle their remaining differences over rice aid, test runs for cross-border railways and other issues during their final day of economic cooperation talks Saturday.

The two sides were originally scheduled to issue a joint press statement at 2 p.m., but they are still engaged in a series of working-level negotiations to work out the wording for the statement's final draft, according to reports from Pyongyang, where the talks are currently under way.

South Korean officials said the two sides agreed on when test runs will be held for the cross-border railways but stopped short of revealing a date, only saying that the tests will be conducted some time in mid-May.

High on the agenda of the talks are a military safety guarantee for the railways, South Korea's resumption of rice aid to the North, and the South swapping raw materials for natural resources from the North.

Although it had already been agreed upon during the last ministerial meetings held in March, rice aid again became a contentious issue. The North requested the delivery of 400,000 tons of rice from the South as soon as possible, but South Korea is pushing to link the issue with the North implementing initial steps toward its nuclear dismantlement.

The South suspended food and fertilizer aid shortly after the North conducted missile tests in July. But fertilizer aid was resumed in late March, a few weeks after the two sides agreed to patch up their strained relations.

As for expanding economic ties, the North hopes to receive raw materials from the South in exchange for providing its natural resources close to the time when railway test runs are conducted.

But the South made clear that it will provide the North with 80 million dollars worth of raw materials only after the two sides conduct the railroad trial runs. In 2005, South Korea agreed to offer raw materials to the North to help it produce clothing, footwear and soap starting in 2006.

In return, the North was to provide the South with minerals, such as zinc and magnesite, after mines were developed with South Korean investments guaranteed by Pyongyang.