KUNDLI, India (Reuters) - Tens of thousands of farmers on tractors occupied a stretch of an expressway on the periphery of the Indian capital New Delhi on Thursday in one of the biggest shows of strength since they began a sit-in against deregulation of farm markets more than a month ago. Prime Minister Narendra Modi’s government has held several rounds of talks with the farmers to placate them, offering concessions on the three laws it passed last year to bring private investment into the country’s antiquated agriculture markets. But the farmers have resisted the overtures and been camped at an interstate border near the village of Kundli outside Delhi for more than 40 days demanding the government withdraw the laws. On Thursday, the protesters mostly from the Sikh-dominated northern state of Punjab, which is one of the country’s leading producers of wheat and rice, took to the highway. Turbaned young men and elderly farmers with flowing beards rode a convoy of tractors numbering in the thousands, some with loud music blaring. There was no sign of any police presence. “We want Modi to repeal the three laws,” said Rajvinder Singh, 35, a farmer from Punjab’s Gurdaspur district. He said the rally was a way to build pressure on the government in the lead-up to India’s Republic Day on Jan. 26 when the farm unions have threatened to march on to the centre of the capital if the laws are not revoked by then. Farmers fear that the deregulation under which food processors and big retailers can directly buy produce from them will eventually replace government-regulated wholesale markets where they are guaranteed a minimum price for their produce. The government says the state-regulated market yards will continue alongside the new ones and has offered to give written assurances to the farmers they will continue to get a minimum price. On Friday, the two sides will sit down for another round of talks.