New Delhi, Feb. 9: Foreign secretary S. Jaishankar has asked the Prime Minister's Office to return recommendations for key ambassadorial postings sent by his predecessor Sujatha Singh, signalling the start of what many believe could be the biggest foreign office shake-up in years.

Singh and external affairs minister Sushma Swaraj had sent at least six recommendations for ambassador posts to the PMO in January and were finalising proposals for another 35 key positions that will fall vacant this year.

But Jaishankar, who has also called for files on these other postings, will now go through all recommendations made by Singh before picking what will be his team of ambassadors positioned at key stations, three senior officials familiar with the move said.

The review, the officials said, is also aimed at relocating some senior diplomats who are currently posted at headquarters but who the new foreign secretary is convinced may not be best-suited for their current roles.

"This is just the start, the tip of the iceberg," one of the officials said. "Every recommendation is being looked at afresh. I can't remember when I last saw such an overhaul of past decisions."

Over 40 positions as ambassadors, high commissioners and consuls-general are either currently lying empty or will fall vacant this year. These include those of the high commissioners in Bangladesh, Canada, Australia and the UK, ambassadors in Afghanistan, Iran, Saudi Arabia, South Korea and Indonesia, and permanent representatives to the UN in New York and Geneva.

A new vacancy was created when Jaishankar was plucked out of Washington, where he was ambassador, to head India's diplomatic corps at South Block.

But Prime Minister Narendra Modi did not give his nod to a single recommendation Singh - and Sushma, who backed her proposals - sent, pointing to the distrust that ultimately cost Singh her job.

The Prime Minister had addressed all Indian ambassadors posted abroad at a conclave here on Saturday. But the review of Singh's recommendations by the new foreign secretary suggests Modi has authorised Jaishankar, who he handpicked to replace Singh, to revamp the external affairs ministry. It also underscores the marginalisation of foreign minister Sushma, and her approvals - which concurred with Singh's - within the diplomatic establishment.

The trust of the Prime Minister that Jaishankar enjoys appears to have already sped up the appointment process.

The new foreign secretary, officials confirmed, has picked Navdeep Suri, currently Indian ambassador in Egypt, for the vacant high commissioner's position in Australia.

Vishnu Prakash, the outgoing ambassador in South Korea is expected to shift to Canada, where too the high commissioner's position is vacant after former navy chief Nirmal Verma's term ended in November.

But the shuffle Jaishankar has begun is also expected to cause an upheaval at the foreign office headquarters in South Block.

The foreign secretary, officials said, is likely to shunt out at least one secretary-level officer - just a notch junior to Jaishankar - to a foreign mission, and replace him with a diplomat brought in from an embassy abroad.

The re-jig could also touch diplomats who head geographical divisions within the foreign ministry - joint secretary level officers, some of whom are likely to be posted overseas, and replaced by others.

The uncertainty surrounding Jaishankar's review of past recommendations by Singh has spawned chatter within the diplomatic establishment on the criteria that the Prime Minister and foreign secretary may use to pick their new team.

Jaishankar has indicated to senior diplomats that he would like a "younger" team of ambassadors and high commissioners heading key posts. Currently, most such posts that are not vacant are occupied by diplomats older than Jaishankar or his immediate peers.

But the foreign secretary, officials said, may find himself grappling with a challenge as he oversees a shuffle - the talent at his disposal is drawn from the same pool of about 900 Indian Foreign Service officers his predecessor had access to.

"There's a lot one may want to do but you've got to see who you have," said a second official familiar with the changes Jaishankar is planning. "Ultimately, you have the same set of people the earlier foreign secretary had - the challenge is to use them as effectively as you can.