India and Japan share a strong strategic interest in expanding cooperation on maritime security and promoting regional stability, Indian Prime Minister Manmohan Singh said Tuesday. Ensuring that sea lanes remain open and free is vital for the region's prosperity, given its dependence on oil imports from the Middle East, Singh said on a four-day Japan visit focused on firming up the two countries' economic ties and other cooperation. "India's relations with Japan are important not only for our economic development but also because we see Japan as a natural and indispensable partner in our quest for stability and peace in this vast region," Singh said in a speech quoted by the Associated Press. "We have shared interests in maritime security, face similar challenges to our energy securities. There are strong synergies between our economies, which need an open, rule-based international trading system to prosper," he said. Among other priorities, Japan and India are working toward a deal on nuclear energy cooperation, as Tokyo tries to boost exports of atomic technology and other infrastructure to help revive the economy.