The last time Indian farmers descended on New Delhi, they dealt Narendra Modi a rare political blow, forcing him to backtrack on agricultural reforms.
Now Daljinder Singh Haryaoo, who five years ago drove south to the capital from India's northern Punjab state, has said he will climb back on his tractor if the prime minister's government makes too many concessions on agriculture in trade talks with US President Donald Trump.
"Allowing crops and food products through a trade agreement will finish us," said Singh Haryaoo, one of 30,000 members of a powerful farming union in Punjab's agricultural heartlands. He grows maize and rice, and keeps dairy cows.
Difficult trade negotiations with the US have thrust farmers' complaints to the centre of national debate, with the possibility of a flood of cheap US agricultural imports handing the opposition fresh ammunition to attack Modi.
New Delhi has historically excluded agriculture from trade pacts, arguing such moves would hurt millions of poor farmers, a powerful voting bloc. The prime minister is facing four regional elections within the next seven months and has said he would stand "like a wall" against any policy that threatens farmers' interests.
India has one of the world's biggest agricultural sectors in terms of workforce and output, notably of rice and milk, and successive leaders have been loath to reform the sector.
Agriculture minister Shivraj Singh Chouhan this month hailed agriculture as "the backbone of India's economy, and farmers are its soul; serving farmers is akin to worshipping God".
Nearly half of the workforce in the world's most populous country are employed in agriculture, which accounts for almost one-fifth of Indian GDP.
So great was the anger at Modi's proposed reforms in 2020 that thousands of farmers, including Singh Haryaoo, camped out in New Delhi for nearly a year. The prime minister eventually reversed course on plans to deregulate the trade in agricultural commodities allowing private players to set prices -- a rare policy retreat.
This time round, Modi is facing increasing pressure from the Trump administration. US commerce secretary Howard Lutnick recently criticised India for not importing "a single bushel" of US maize.
India currently imposes tariffs of 70-80 per cent on US rice, 15-50 per cent for maize and 30-60 per cent on dairy products from the country.
It is also one of the countries hardest hit by Trump's trade war, facing 50 per cent tariffs. Trump, who said the higher levies were in response to India's trade in Russian oil, has indicated that Modi would reduce these purchases, if not, he vowed to keep the "massive tariffs" in place. Both leaders are expected in Malaysia for a summit of Asian leaders, which starts on Sunday.
People briefed on the negotiations in New Delhi acknowledge that disagreements over US agriculture are a major "sticking point".
Farming may have been a "red line" for India in other negotiations -- including Australia in 2022, the UK this year and also the EU -- but the US agricultural lobby is pushing particularly hard, said an Indian official familiar with the negotiations.
India might end up having to make some concessions on agriculture to the US, a person familiar with the discussions in New Delhi said after commerce minister Piyush Goyal's visit to Washington late last month. Goyal's team travelled last week to the US to fast-track talks with hopes of closing on a deal this year.
While India is unlikely to open up the farming sector entirely, it could allow imports of some maize for ethanol production and set quotas for other products.
The talks are complicated by the fact that most US maize and soyabean production is genetically modified and India has strict rules on GM output.
Agronomists in the 1960s and 1970s made Punjab a testing ground of improved seeds and better farming, transforming India into one of the world's largest food producers.
But agriculture in India remains largely artisanal with farmers having small, fragmented land holdings -- the average Indian farm comprises just a little over one hectare, compared with more than 180 hectares in the US. In dairy, the average herd size in India is two to three animals per farmer, compared with 380 in the US.
With Indian farming often unprofitable for the hundreds of millions depending on it, Avik Saha, one of the co-ordinators of Samyukt Kisan Morcha, a coalition of dozens of Indian farmers' unions, said: "The farmer is extremely concerned about any import that further pushes the price down. These are all clear, large bold writings on the wall: for the farming sector, a free trade agreement is unimaginable."
If the government makes compromises against farmers' interests, then voters will "drag it down", said Mohini Mohan Mishra, the general secretary of the Bharatiya Kisan Sangh, the farmers union linked to the Rashtriya Swayamsevak Sangh, the Hindu nationalist group and ideological parent of Modi's Bharatiya Janata party.
Some of India's largest farming lobbies have also weighed in.
With almost 200,000 co-operative societies and employing some 80mn people, dairy is not only an important constituency. It is also sensitive because of concerns US cattle are fed with animal byproducts, contrary to Indian dietary and religious habits.
Rupinder Singh Sodhi, president of the Indian Dairy Association, said: "India does not need dairy from outside. We are the world's largest milk producer."
Ajay Bhalothia, general secretary of the All India Rice Exporters' Association, has asked Indian trade negotiators to "put pressure on the US to remove tariffs on Indian rice, but they told us that America wants their rice to be made duty free in India -- that is not viable for India".
For the chair of the Farmers' Forum India, Ajay Vir Jakhar, "India will never be able to compete with subsidised US" farming products, such as maize and milk, which would "destroy the livelihood of millions of small" Indian farmers.
Back in Punjab, the strength of feeling is apparent in the "no farmer, no food" slogan emblazoned on many trucks. Singh Haryaoo argues that "our entire farming and livelihood are at stake". If Modi opens India's market to subsidised US products such as rice, maize and dairy "we would hold a much bigger protest", said Singh Haryaoo.