The expression of regret to be delivered in Gisborne today for deaths of Maori at the first encounter of Captain Cook was requested by the iwi themselves, a British High Commission spokesman said.
"The expression of regret responds to a request from the local iwi for this history to be heard and acknowledged," the statement said.
"The British High Commissioner will acknowledge the pain of those first encounters, acknowledge that the pain does not diminish over time, and extend her sympathy to the descendants of those killed."
Both James Cook and botanist Joseph Banks had written in their diaries of their regret at the deaths, the statement said.
"It is not how any of us would have wanted those First Encounters to have transpired. "
Laura Clarke, the British High Commissioner, is in Gisborne for two private meetings today: first with Ngāti Oneone about midday, and then with the three Tūranga iwi: Ngai Tāmanuhiri, Rongowhakaata, and Te Aitanga a Māhaki a few hours later.
Some of their ancestors were among the nine Māori killed or wounded in Cook's first landing in New Zealand in 1769, the grief for which has endured through generations.
She is expected to make a verbal expression of regret and nothing will be put in writing.
The intention is that the expression of regret becomes part of the history of the iwi concerned and that they determine how it is shared and with whom.
The statement said the commission had worked with the iwi for many months to prepare for the meeting.
"We see this as the beginning of a longer process, and forward-looking relationship between these iwi and the UK."
The UK wanted the closest possible relationship with Aotearoa New Zealand.
"That means with both Pākeha and Māori, with the Crown and with all the iwi of Aotearoa.
"At the British High Commission, with the help of our pou ārahi Māori - Māori engagement adviser, we are building our understanding of te ao Maori, building relationships with iwi and hapū, cultural associations and trade networks, to forge a future relationship together, beneficial to both our countries and all our people.
"The British High Commission has established a formal relationship with the Federation of Māori Authorities [FOMA] and has hosted a Whaariki Tāmaki Māori Business Networking event in partnership with EY Tahi, with the aim of increasing two-way trade and investment between Māori and the UK."
The UK was exploring opportunities for education and cultural exchanges and will lead a delegation to London in November to launch He Whai Te Matauranga, a scholarship programme facilitating greater access to Māori to taonga held in UK institutions.
In a statement, Minister for Māori Crown Relations Kelvin Davis said this was a significant day for Tūranga and Ngāti Oneone and acknowledges the sense of loss they still feel.
"This is a matter between Tūranga Iwi and the British High Commission, and this day is about them - so it wouldn't be appropriate to comment further.
"The Government provides Crown apologies for past actions through the Treaty settlement process, as that is the most meaningful way of saying sorry to the iwi and hapū affected."