Sri Lanka says it will resettle most of the 280,000 Tamils displaced by the recently ended war within six months.
The pledge was made after President Mahinda Rajapaksa met the Indian Foreign Secretary Shivshankar Menon and India's national security adviser.
Their joint statement underlined the urgency of relief and resettlement measures, but also of achieving a "lasting political settlement".
The plight of those forced out of their homes has caused widespread concern.
Aid groups complain their access to the displaced camps has been greatly restricted, and some reports had suggested the government was willing to hold the displaced there indefinitely.
The government says remaining pockets of Tamil Tiger rebels need to be weeded out and infrastructure rebuilt before civilians can return to their homes.
India is keenly interested because Sri Lankan Tamils have close links to the millions of Tamils who live in the southern Indian state of Tamil Nadu.
The joint Sri-Lankan-India statement said it was time to "focus attention on issues of relief, rehabilitation, resettlement and re-conciliation" in Sri Lanka.
It said both sides were co-operating in providing humanitarian relief to the estimated 280,000 people displaced in the final government offensive against Tamil Tiger rebels this year.
But it said the need to resettle the displaced in their villages and towns was urgent, and to this end "the government of Sri Lanka... outlined a 180-day plan to resettle the bulk of IDPs [internally displaced persons] to their original places of habitation".
The government of India "committed to provide all possible assistance in the implementation of such a plan in areas such as de-mining, provision of civil infrastructure and reconstruction of houses", the statement said.
International aid agencies have pleaded for relief workers to have better access to the tightly controlled camps - which the government calls "welfare villages", but which the Tamil Tigers deem "concentration camps".
Earlier, Sri Lankan Minister for Resettlement Rishat Badiuddin told the BBC Sinhala service the government would try its best to meet the six-month deadline.
But he said landmines had to be cleared and documentation obtained that the areas were risk free.
The statement added that both countries realised the "urgent necessity of arriving at a lasting political settlement in Sri Lanka".
It said that Colombo also intended to start a broader dialogue with all parties including Tamil ones, "for further enhancement of political arrangements to bring about lasting peace and reconciliation in Sri Lanka".
Earlier, the Indian representatives told reporters that President Rajapaksa was willing to go beyond a 1987 devolution plan in order to consolidate peace in the ethnically divided nation, where at least 80,000 people have been killed in three decades of war.
Reconciliation Minister Vinayagamoorthi Muralitharan, a former rebel commander who was known as Col Karuna, earlier said elections would be held in areas affected by recent fighting once displaced people had been resettled.
He said the polls would address the grievances of the Tamil minority.
Mr Muralitharan said he wanted Tamils to have a greater role in parliament.
"If we sit on the opposition side we will never get any benefits for the minority community," he said.
The BBC's Charles Haviland in Colombo says much of the north-eastern area is now depopulated and with the problems of minefields and other land development issues, a huge rehabilitation process will be needed before elections can take place.
Last year, Mr Muralitharan's party won a landslide victory in local elections in and around Batticaloa, south of the recent conflict zone, the first polls to be held there in 10 years.
When Mahinda Rajapaksa won the presidency in 2005, there were virtually no votes cast in the Tamil areas in the north-east - turnout in Jaffna was put at 0.014%.
The Tamil Tigers denied disrupting elections but officials complained of heavy intimidation.
Some members of the Tamil minority, and a group of leftist parties, say Tamils and Muslims have in some cases been harassed or insulted or forced to dance by people celebrating in the streets.
On Thursday, Mr Rajapaksa called for an end to ethnic divisions.
"I see it as the duty of all to ensure that all differences that hitherto divided our people are subsumed in the great and momentous joy that is shared by us all.
"The celebration of this victory, as deep as it is felt, should be expressed with magnanimity and friendship towards all," he said.
His call was perhaps an indication, our correspondent says, of the sensitivity of the end of this war with its ethnic origins.
On Tuesday, the president declared the country "liberated" from Tamil Tiger rebels after the last pocket of territory held by them was taken.