He was speaking on his flight from St Petersburg where he attended the G8 summit.
"The political process in the US knows our concerns and they will be taken into account," he said.
On why the government was going public with this information now, Dr Singh said the government never said that it did not have any concerns.
"We said the July 18 Joint Statement and the separation plan should be the guiding factors for the legislation. We cannot take any more commitments that are not explicitly stated in the statement. The broad parameters are clearly spelt out in the agreement. The US President (George W Bush) gave a clear message that there would be no shifting of the goal post," Dr Singh added.
On the status of the dialogue with Pakistan, the prime minister said at the time being, the process has suffered and "we will look at whatever options there are."
Without referring to it as a setback, Dr Singh said the dastardly tragedy in Mumbai and Jammu and Kashmir should reflect on the relations.
"I have always believed that the destinies of the people of South Asia are interlinked and to realise our potential we need peace and stability," he said.
Speaking on the assurance he had received from the leaders of G8 for India's fight against terrorism, he said fighting terrorism was not a one-way process but a long drawn one.
"We have to operate at several levels, strengthen our intelligence machinery and disaster management," the prime minister conceded.
Responding to a question on how the words 'War on Terror' had entered his vocabulary the prime minister said the tragedy in Mumbai was enormous. "It was an onslaught that has to be met with full force and determination."
He also said he hopefully would have a full-fledged foreign minister soon.
On his pitch for United Nations Under Secretary General Shashi Tharoor as a candidate for secretary general in his meetings with world leaders, the prime minister said, "It would not be an easy fight, but since it is Asia's turn and the next chance will come after 40 years, we thought it was important for India to put its candidate in front of the world."
Dr Singh called Dr Tharoor an outstanding candidate who had great experience in the area of peacekeeping and refugees and that he had been a part of the UN for 30 years.
He said the leaders he spoken to had no doubt about Dr Tharoor's high credentials but Dr Singh added that as of now "we can't say the job is in our pocket."