The plans include a new embassy in Djibouti.
"We have to reinvigorate and expand British diplomacy".
"Our network of friendships is unparalleled", he said.
For the first time, some of these jobs will be available to non-civil servants.
British ambassadors are traditionally civil servants, often with a long career in the diplomatic service.
"But we must never close our eyes to the approaches and skills of other industries". "In the past you may have heard of retrenchment and retreat, not anymore", Hunt said, adding that he would also open up "one or two" ambassador posts a year to those outside the civil service, particularly business people. He previously served David Cameron's government as Downing Street chief of staff.
Hundreds of new diplomatic positions overseas, additional personnel, and teaching of extra languages by the Foreign Office - are all on the department's agenda to be announced by the Foreign Minister Jeremy Hunt.
"No-one will object to this being done in a small way, more than that and it will send a very bad signal", Lord Ricketts told Sky News.
Woody Johnson, the U.S. ambassador to the United Kingdom, is a businessman who was nominated by President Donald Trump. The addition includes 335 diplomatic posts overseas, 328 new roles in London, and 329 new "locally engaged" staff.
Mr Hunt is proposing the largest creation of new postings in a generation, confirming 12 new diplomatic outposts and almost 1,000 more personnel, include 335 overseas posts, 328 London-based roles and 329 locally engaged staff.
Many of these moves have previously been announced.
Priya Guha, a former consul general in San Francisco who left to work in the private sector, told the BBC that the skills of the diplomat, "like influencing, negotiating, leadership, management, operational excellence", are highly valued in the private sector and "it's really valid for the Foreign Office to look at how can we bring some of those diverse range of skills and experiences back" into the service as well.
Additionally, the Foreign Office will teach 20 extra, including Kazakh, Kyrgyz, Shona and Gujarati.
The foreign secretary will say that the UK's network with countries around the world is underpinned by the shared values of democracy, the rule of law and a belief in free trade.
"When these values are under threat, Britain's role - indeed obligation - is to defend them".
Asked by the BBC ahead of the speech whether the move was a step towards a US-style system which allowed "cronyism", Mr Hunt said: "There will be absolutely no conflict of interest allowed and anyone applying for these jobs will apply through normal Foreign Office processes so we can make sure that proper independence is protected".