The United States called Wednesday on all nuclear powers to exercise restraint, but stopped short of criticizing growing partner India which plans to test a new long-range nuclear-capable missile.

Asked about the missile which could strike deep into China, State Department spokesman Mark Toner said that the United States was aware of the test plans but has not "specifically" raised the issue with India.

"I just would say that we urge all nuclear-capable states to exercise restraint regarding nuclear capabilities. That said, India has a solid non-proliferation record," Toner told reporters.

India hoped to test the new Agni V on Wednesday evening from the eastern state of Orissa on the Bay of Bengal, but bad weather forced it to postpone the launch until Thursday or Friday.

The Agni V has a range of 5,000 kilometers (3,100 miles). India first tested nuclear weapons in 1998 and officials at the time said the chief concern was fellow Asian giant China -- not historic rival Pakistan, which followed with its own nuclear test.

The United States in recent years has rarely criticized India other than on commercial issues as US leaders seek to build a closer partnership between the world's two largest democracies.

Some analysts say that the momentum in US-India ties has slowed down in recent months amid economic disputes and Washington's concern over India's continued oil imports from Iran.