By Shahzeb Jillani
BBC South Asia reporter, Washington
The revelation by a scientific monitoring institute in the United States that Pakistan is building a powerful new nuclear reactor has left many in Washington and Delhi wondering.
Isis argues that the plant could trigger a new arms race
Could it be that the report by the Washington-based Institute for Science and International Security (Isis) was released at a time when it may derail the US-India nuclear agreement?
The landmark deal allowing the US to sell civilian nuclear technology to India - for the first time in three decades - is expected to be ratified soon by the US Congress.
Nervous supporters of the deal see the report, which says that Pakistan is capable of using the reactor to produce enough plutonium to make 40 to 50 nuclear weapons a year, as the "final attempt by the US nuclear non-proliferation lobby" to raise paranoia over the prospect of a nuclear arms race in South Asia.
They argue that the Isis report is aimed at influencing US lawmakers to insist upon tightening certain provisions in the bill, or even the introduction of amendments which may jeopardise its approval all together.
Pakistan - like India - has not signed the nuclear NPT
But even if the arguments about the timing of the report are accepted, the influence it could have on the future of US-India nuclear deal - or on the sale of or F-16 fighters to Pakistan - may be somewhat exaggerated.
It has to be remembered that Isis is an institution committed to "stopping the spread of nuclear weapons".
In the past, it has published investigative reports on covert nuclear activities of countries like Iran, North Korea, India and Pakistan.
In its latest report on Pakistan, the organisation used satellite photos and other data to bring the country's nuclear site at Khushab to the world's attention.
The authors, David Albright and Paul Brannan, believe that with a capacity of 1,000 megawatts or more, the heavy water reactor has the potential to create a "new escalation in the region's arms race".
But some of the reasoning behind this conclusion could be flawed.
The report states that construction on the reactor began nearly six years ago in March 2000.
But this was a time when the chances of an US-India nuclear deal were slim to non-existent.
According to Naeem Salik, South Asian security analyst and guest scholar at the Brookings Institution, both Pakistan and India have been working on modernising their nuclear arsenal with or without the US-India nuclear deal.
The US wants Pakistan on its side in the 'war on terror'
"This only goes to show that Pakistan's determination for achieving minimum credible deterrence against India cannot be underestimated," he said.
Nevertheless, it is true to say that the Isis report may have caught many Indian and US lawmakers by surprise.
The Bush administration, however, was not caught out so easily, and publicly reiterated its support for the nuclear deal with India.
"We have known of these plans for sometime," said White House spokesman Tony Snow.
He pointed out that Pakistan - like India - has not signed the nuclear Non-Proliferation Treaty (NPT).
"Yet we continue to discourage the expansion and modernisation of nuclear weapons programmes, both of India and Pakistan," Mr Snow said.
During the course of lobbying the US Congress in favour of the nuclear agreement, Bush administration officials consistently argued that the deal would not end up feeding India's nuclear weapons programme, or start a nuclear arms race in the region.
Security experts argue that is why the White House has not wavered in its support for the deal: It thinks that Pakistan's desire to expand its nuclear arsenal is not dependent on the agreement with India.
"I do not believe that the concerns of an arms race in the report will have any impact when it comes to Congress for passing the US-India nuclear agreement, or for that matter, the US-Pakistan F-16 sale," maintains Christine Fair, South Asia expert and Senior Research Fellow at the United States Institute of Peace.
So as revealing as the Isis report may be, it is unlikely to influence the long-term strategic vision of the US for South Asia.
The Bush administration is determined to build a lasting economic, political and military partnership with the "biggest democracy in the world".
It also wants the only Muslim country armed with nuclear weapons on its side in the "war on terror".
So this is a week that began with the release of a report raising the frightening possibility of a nuclear arms build-up in South Asia.
It looks as if may well end with the US more determined than ever to go ahead with its nuclear agreement with India and with the sale of F-16 jets to Pakistan.