The unexpected thaw in Indian-Pakistani relations is welcome, even if many old ice dams threaten this latest détente.
Indian Prime Minister Atal Behari Vajpayee opened the door two weeks ago with a surprise speech, saying he wanted to "extend the hand of friendship" to Pakistan. Islamabad quickly responded; the two nations say they will exchange ambassadors and resume air links. Working-level talks may begin soon on a possible summit.
The two nations, which share history, culture, several languages, and a mutual animosity, have fought three wars since they were carved out of British India in 1947. Most of the tension involves a dispute over Kashmir. The divided border province, mostly occupied by India, is that country's only Muslim-majority state.
The mutual distrust has led both nations to reject the Nuclear Non-Proliferation Treaty and to develop small arsenals since 1998, resulting in a perilous nuclear standoff. The two were on the brink of war last year, raising deep concern worldwide.
Mr. Vajpayee and Pakistani President Pervez Musharraf both face stiff domestic opposition to any concessions from religious hard-liners. Hindu nationalists - the backbone of Vajpayee's BJP party - reject any compromise over Kashmir and see India's A-bomb as a great achievement. Sunni-Muslim militants in Pakistan embrace jihad to "liberate" Kashmiri Muslims. Terrorists trained in Pakistan have killed thousands of Indians in Kashmir and elsewhere.
Vajpayee's initiative may be driven by India's increasing dependence on foreign investors, especially from the US, who won't stick around if war always looms.
Pakistan has repeated its offer to abandon nuclear weapons if India does. But India's nuclear-arms program is driven as much by a perceived threat from nuclear China as by friction with Pakistan or Hindu jingoism. A friendlier Pakistan won't solve these problems but could defuse tensions.
Islamabad is signaling a more flexible approach than it took at a failed 2001 summit. The two leaders should begin with graduated confidence-building steps to prepare for a summit. Such steps would best include a Pakistani crackdown on militants and terrorist infiltrations. As trust grows, the two countries will be better able to discuss their deepest differences.