Ignoring diplomatic protocol, US Secretary of State John Kerry had telephoned National Security Advisor Shivshankar Menon to discuss the row over the arrest of an Indian diplomat after he was told that his Indian counterpart Salman Khurshid was busy in Parliament.

Flying back to the United States from a crucial Asia Pacific trip, Kerry, telephoned Menon, from his plane yesterday as Khurshid was busy in the proceedings of the Parliament.

Since Kerry was flying back to the US on his plane, technically, there was a little window for him to make a phone call to India, sources said.

But, given the sensitivity of the nature of relationship between the two countries in the aftermath of the arrest and alleged mistreatment of Devyani Khobragade, India's Deputy Consul General in New York, sources said the Secretary of State did not want to wait till he landed in the US.

As such Kerry decided to speak directly with Menon, who was available at that time, even though the latter was below his diplomatic protocol.

Last week, Kerry had spent some 15 minutes with visiting Indian Foreign Secretary Sujatha Singh, ignoring normal diplomatic protocols.

This is because, sources, said he values the relationship with India and his commitment to strengthen and deepen Indio- US ties.

According to State Department Deputy Spokesperson Marie Harf, as a father of two daughters about the same age, Kerry "empathises with the sensitivities" that he heard from India about the events that unfolded after the arrest.

"And in his conversation with National Security Advisor Menon, he expressed his regret as well as his concern that we not allow this unfortunate public incident to hurt our close and vital relationship with India," Harf said.

Kerry, she said, is being kept updated on the developments.

"He's been kept up to speed on this case," she said.

The White House too kept  US President Barack Obama informed about the latest development on the Indio-US bilateral ties, his spokesperson, Jay Carney, told reporters at his daily news conference.