LIMA, Dec 2 (Reuters) - Dozens of buses and trucks on the largest highway in southern Peru were stranded on Wednesday as farm workers launched a third day of protests, forcing lawmakers to promise fresh debate over a long-standing but controversial agrarian law.

The protesters, whose demands include higher wages, have since Monday blocked the Panamericana Sur highway 300 km (190 miles) south of Lima, leaving trucks carrying fresh fruits and vegetables at a standstill.

Peru's ministers of agriculture and labor met with leaders of the farm workers movement on Wednesday but have yet to reach agreement to halt the demonstrations.

"It is important to prioritize dialog so that we do not generate consequences that we could later regret," said Interior Minister Rubén Vargas. He called on protesters to clear the roadway.

Lawmakers on Wednesday said they would debate changing, or even scrapping all together, the agriculture promotion law contested by the farm workers.

The legislation is widely seen as having helped spur investment and the sector's development. But workers say the gains have come at their expense, leaving them with too-low wages and paltry benefits.

Agro-exports have become the second largest generator of foreign exchange in Peru in recent years, after mining, according to the Association of Agricultural Producers Guilds of Peru (AGAP).

Peru, a tropical country in the southern hemisphere, is the world's leading exporter of blueberries, but also ships fresh grapes and avocados to China, the United States and Europe.

The sector went largely unscathed during the coronavirus outbreak, largely because it was exempted from restrictions that hobbled mining and fishing, among other industries. (Reporting by Maria Cervantes, writing by Dave Sherwood Editing by Marguerita Choy)