U.S. Deputy Secretary of Defence Ashton Carter, who played a critical role in boosting Indo-U.S. defence ties, said on Friday that he will step down in December.

Mr. Carter, the Pentagon’s number-two ranking official, in his resignation letter, simply stated that “it is time for me to go” but did not give a specific reason for leaving the Obama administration.

“Earlier today, I met with Ash Carter and reluctantly accepted his decision to step down as Deputy Secretary of Defence on December 4th, after more than four and a half years of continuous service to the Department of Defence,” Defence Secretary Chuck Hagel said.

Mr. Carter, 59, started serving as the deputy from October 2011 under former Defence Secretary Leon Panetta. The Pentagon did not give any reason for his resignation.

In October 2011, he was promoted to the Pentagon’s second-ranking civilian official by Mr. Panetta. He was among those the White House considered to take over when Panetta announced his retirement at the end of U.S. President Barack Obama’s first term. But Mr. Hagel, a Vietnam war combat veteran who served with Mr. Obama in the Senate, had superior political credentials.

“The decision to depart the Pentagon later this year was Deputy Secretary Carter’s and his alone. He’ll be missed by the Secretary. They’ve had a strong and effective working relationship and friendship that will continue for the next two months and beyond,” Pentagon Press Secretary George Little said.

The announcement was made at a senior Pentagon leadership staff meeting, where Mr. Carter received a standing ovation from Mr. Hagel and the rest of the leadership team, Mr. Little said.

Mr. Hagel described Mr. Carter as an extraordinarily loyal and effective Deputy Secretary.

“He possesses an unparalleled knowledge of every facet of America’s defence enterprise, having worked directly and indirectly for eleven Secretaries of Defence over the course of his storied career,” Mr. Hagel said.

Mr. Carter visited India in September and was instrumental in the path-breaking Carter-Menon initiative with National Security Advisor Shivshankar Menon, under which the two countries have decided to jointly develop and produce high-technology defence equipment.

A former Harvard professor and Rhodes scholar who earned a doctorate in theoretical physics from Oxford University, Mr. Carter served at the Pentagon during Bill Clinton’s presidency in the 1990s and is deemed an expert on arms control.

In his resignation letter, Mr. Carter said he had long planned to wrap up his tenure on December 4, but had postponed making the announcement due to the “turbulence surrounding the fiscal situation”.

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