When Sri Lanka slid into its worst economic crisis in seven decades leading to deadly riots and alarming shortages of fuel, food and medicines earlier this year, its giant northern neighbor stepped into the breach.

India provided about $4 billion in rapid assistance between January and July, including credit lines, a currency swap arrangement and deferred import payments, and sent a warship carrying essential drugs for the island's 22 million people.

Now, as Sri Lanka closes in on a $2.9 billion loan deal from the International Monetary Fund (IMF) and its economy stabilizes, India is seeking to land ambitious long-term investments, with an eye on countering the influence of regional rival China, a government minister and three sources said.