Senior executives of Honda Motor Co., Japan's No. 2 carmaker, will arrive at a Honda supplier's plant in south China on Sunday to negotiate with workers, sources told Xinhua. [Full coverage about Honda strike]

An ongoing strike over pay entered its fourth day on Saturday and threatens the company with having to halt its assembly lines.

About two-thirds of the 1,400 workers at Honda Lock (Guangdong) Co., Ltd. refused to return to the workplace on Saturday as negotiations with management showed no signs of progress, sources said.

Also, the company allegedly threatened to fire workers if they continued their walkout beyond June 15, stoking tension at the plant.

The Honda plant is located in Zhongshan City in China's manufacturing hub of Guangdong, which has become the center of a wave of labor unrest in recent weeks.

Liu Zhiwei, a local government publicity official, said Saturday that top Honda executives would be arriving in Zhongshan to meet with striking workers in a bid to break the deadlock.

No details are available and Honda officials were not able to confirm information about its top executives' schedules.

On Friday, workers held a rally in front of the factory, enraged by a company notice threatening dismissals unless workers signed a pledge to end the strike.

Tension built up again on Saturday as the company threatened striking workers with an ultimatum to end the strike by June 15 or be fired, said Dong Zuwen, deputy mayor of Xiaolan township, where the plant is based. However, the threat has not been confirmed by company officials.

Workers' representatives and government officials feared the tension could escalate into a clash.

However, workers did not hold the rally on Saturday. Rather, some striking workers decided to quietly wait for the arrival of the top Honda officials.

Honda Lock (Guangdong) Co., Ltd., a joint venture between the Japanese firm and a local company affiliated with the Xiaolan township government, employs 1,400 workers and supplies Honda vehicle assembly plants with locks and key sets.

The lock factory had earlier agreed to increase each employee's monthly salary by 100 yuan (14.6 U.S. dollars) and to raise the standard of over-time pay to 50 yuan (7.3 U.S. dollars) per day, but the offer was short of the striking workers' demand for about a 500 yuan (73 U.S. dollars) increase per month.

This was the third strike to hit Honda's suppliers in Guangdong in less than a month. Workers at two other factories demanded, and received, significant pay increases.