The authority will on Saturday start public consultation on proposed planning changes which would allow new diplomatic embassies to be built on land in Curtin, which include the North Curtin horse paddocks.

At the request of the ACT government, it is also proposing to reclassify part of one of those blocks to enable future residential development off Yarra Glen Road - which is on the route of the planned City to Woden light rail line.

After it was accused of secrecy over the deal to secure the Curtin blocks, National Capital Authority chief executive Sally Barnes said the NCA was "genuinely" seeking the community's input as it sets about creating a new "world-class diplomatic estate".

The National Capital Authority has put forward the proposed planning amendment after securing the Curtin blocks in a deal with the ACT government, which saw the territory receive land needed for the redevelopment of Lake Burley Griffin's west basin waterfront.

The authority had been trying for years to secure extra land for new embassies, with a lack of available sites forcing it to turn away countries looking to establish a diplomatic presence in Australia's capital.

The National Capital Plan dictates that new embassies should be built in places which are prestigious and close to Parliament House as well as other embassies, which effectively limits the options to blocks of land in the tightly held inner south.

The selection of the two Curtin sites - which encompass a combined 31 hectares - nevertheless came as a shock to the community, who were unaware about the deal until it was reported in The Canberra Times on March 25.

The authority notified horse owners about the deal two days earlier. The March 23 letter also advised that horses would be allowed to remain at the Curtin paddocks until at least 2022.

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The ACT Equestrian Association was reportedly shocked and angered to have been kept in the dark about the deal, in part because the ACT government had agreed in 2014 to consult early on with the group about issues which might affect them.

A grassroots campaign to save the horse paddocks has been running for weeks, with an online petition attracting more than 1160 signatures.

Ms Barnes would not be drawn on whether she was anticipating significant community opposition to the rezoning. Instead, she expressed hope that local residents, and the wider Canberra community, would see the proposal as a "wonderful outcome for the capital".

She again stressed the importance of the Commonwealth being able to provide land for new embassies in the nation's capital.

"It is one of the main jobs of the National Capital Authority to make sure that the Commonwealth can do its job in Canberra," she said.

"One of its main roles is being able to support diplomatic communities."

Ms Barnes said the rezoning wasn't a done deal, noting that it would require approval from the authority's board and the territory and federal governments before it could proceed.

The authority will prepare a master plan for the diplomatic precinct, which it believes will be large enough to meet demand for embassy land for the next 25 years.

While the strip of land fronting Yarra Glen Road would remain in the territory's hands, future residential development on the site would be subject to strict oversight from the authority, according to its proposal.

Ms Barnes has all but ruled out residential towers on the site because of security implications for the embassies. She said the height and design of any future residential development would need to suit the character, and security requirements, of the diplomatic estate.