Unionized workers at Chilean mining company Minera Escondida Ltda. expect the company to respond to their contract demands by July 5, a union leader said Thursday.

The workers handed the company their demands last Thursday and so far hadn't had any comments from the company, Escondida union treasurer Pedro Marin told Dow Jones Newswires.

The sole union at Chilean copper mine Escondida seeks a 13% pay increase and a $29,299-per-person bonus, the union said Wednesday.

The 2,055 miners that make up the union and represent 97% of union-eligible workers at the mine argue that the city of Antofagasta is the second most expensive in the country and that their wages must be adjusted accordingly.

The bonus sought as the sum of a copper-price bonus and the end-of-conflict bonus miners usually receive after successfully completing negotiations represents 5.4% of Escondida's first-quarter profits, the union said recently.

The miners' contracts expire Aug. 2.

In their previous contract negotiations in 2003, when copper prices averaged $0.66 a pound, Escondida workers obtained a 1.5% wage increase.

Copper prices have soared since mid-2003, with periodic labor disputes contributing to price spikes. In recent months, copper has hovered over $3 a pound, reaching a record $4.00 a pound mid-May.

A strike, however, isn't immediate as according to Chilean labor laws, a walkout could only start after contracts expire. The law also allows for two five-day mediation periods after the contract expiration date to avert a possible strike.

Escondida is the world's largest privately owned copper mine. It produced 1,271,472 metric tons of copper last year, as well as 182,472 ounces of gold.