The action, watched by security forces clad in riot gear, came after farmers' groups rejected a government proposal this week for five-year contracts and guaranteed support prices for produce such as corn, cotton and pulses.
The farmers, mostly from the northern state of Punjab, have been demanding higher prices backed by law for their crops. They form an influential bloc of voters Prime Minister Narendra Modi cannot afford to anger ahead of general elections due by May.
Authorities have thrown up barricades to keep protesters at a distance of nearly 200 km (125 miles) from New Delhi for more than a week, but police said the heavy machinery at Wednesday's gathering was intended for use in damaging them.
"It is not right that such massive barricades have been placed to stop us," said one of the farmer's leaders, Jagjit Singh Dallewal. "We want to march to Delhi peacefully. If not, they should acede to our demands."
Late on Tuesday, Haryana police's chief ordered the immediate seizure of the heavy equipment to prevent its use by protesters in destroying barricades.
Sunday's government proposal of minimum support prices to farmers who diversify their crops to grow cotton, pigeon peas, black matpe, red lentils and corn was rejected by the protesters, who wanted additional foodgrains covered.
Similar protests two years ago, when farmers camped for two months at the border of New Delhi, forced Modi's government to repeal a set of farm laws.
