NEW DELHI (Reuters) -- A top U.S. official will visit India this week to make a fresh attempt to break a deadlock over a controversial nuclear energy deal, an Indian Foreign Ministry official said on Monday.

U.S. Undersecretary of State Nicholas Burns, the main U.S. negotiator for the deal, will hold talks with Indian officials in New Delhi on May 31 and June 1 to resolve differences that have threatened to sink the landmark pact.

"Hopefully, they will be able to make more progress," the official, who did not want to be named, told Reuters.

The deal, first agreed in principle in 2005, has become a symbol of the growing friendship between the two countries.

It aims to overturn three decades of U.S. sanctions on nuclear trade with India to help it meet its soaring energy needs even though New Delhi has not signed the nuclear Non-Proliferation Treaty and tested nuclear weapons.

It was approved by U.S. Congress in December but the two countries have struggled to conclude a bilateral pact that is required to govern nuclear trade due to India's refusal to accept new terms included at the instance of American lawmakers.

The main objections have centered on Washington ending nuclear cooperation if India conducts another nuclear test, and giving India rights to reprocess spent fuel.

The deal has been hit by controversy from the start with critics in both countries saying their governments were giving away too much to the other side.

However, senior Indian officials have said that the political leadership in the two countries remained solidly behind the agreement and would ensure that it clears the hurdles it faces.

Last week, Burns said in Washington that there had been some backsliding on the agreement and that both sides must compromise in order to close the gaps.