Pakistan would review a unilateral ban on testing nuclear weapons if India were to conduct a nuclear test, Pakistan has said.
Old rivals India and Pakistan conducted tit-for-tat nuclear tests in 1998 but neither side has tested since then.
The question of an Indian nuclear test has arisen in connection with a landmark civilian nuclear cooperation deal with the United States, and what the United States would do if India were to conduct a test.
While India has not proposed a resumption of nuclear tests, Indian Foreign Minister Pranab Mukherjee said last week India had the "sovereign right to test and would do so if it is necessary in the national interest".
Pakistani Foreign Ministry spokeswoman Tasnim Aslam did not refer to Mukherjee's comment but said Pakistan viewed seriously "assertions by the Indian leadership about the possibility of resuming nuclear tests".
"This should be a source of concern not just to Pakistan but to the international community as well," she said.
Both countries, which have fought three wars since their independence in 1947, have adopted unilateral moratoriums on testing, but Pakistan would review that in the event of an Indian test, Aslam said.
"Resumption of nuclear test by India would create a serious situation obliging Pakistan to review its position and to take action, appropriate and consistent with our supreme national interest," she said.
India needs to secure the approval of the International Atomic Energy Agency the backing of the 45-nation Nuclear Suppliers Group, which governs nuclear commerce, after which the U.S. Congress needs to vote on the deal for it to go through.
Under the deal, India will get access to U.S. nuclear fuel and equipment for the first time in three decades despite having tested nuclear weapons and not signing the Non-Proliferation Treaty (NPT).
Pakistan was also concerned about the possibility of Australia exporting uranium to India after Australia this month reversed a policy of selling the nuclear fuel only to NPT signatories.
India has been lobbying Australia for access to its uranium.
"Any development that can impinge on the strategic balance in South Asia is a vital concern to us," Aslam said, in response to a question about the possibility of India acquiring Australian uranium.
"Pakistan does not want a nuclear arms race in the region but at the same time we are commited to maintain a credible minimum deterrent," she said.
