The Landcruiser she was driven away in had been flown in on Thursday in the cargo plane and had reinforced windows and pillars.
Mrs Clinton is at the forum for only a day. Her first appointment will be a breakfast with the forum leaders at Trader Jacks, in the capital, Avarua.
She will then hold one-on-one talks with Prime Minister John Key and Mr Puna.
Mr Key said he expected to discuss Afghanistan with Mrs Clinton.
New Zealand and Australia have lost soldiers in Afghanistan in the past few weeks. New Zealand is expected to withdraw its troops next April.
Mr Key also expects to touch on climate change with Mrs Clinton, and get her take on global hotspots.
Mrs Clinton's visit is seen as an attempt by the US to recoup some lost ground from China, which has ramped up its involvement in the Pacific.
Although the US has put a stronger focus on the Asia-Pacific region under President Barack Obama, much of that focus has so far gone on Asia.
Mrs Clinton is expected to reinforce the long US involvement in the region - including in World War II - and announce new aid initiatives.
She will be part of post-forum talks for the so-called "dialogue partners" - non-member countries with an interest in the region.
China is another of those countries - and although it was possibly inadvertent, the timing of Mrs Clinton's arrival in Rarotonga caused competition between the two big powers: it coincided with a press conference by China's Vice-Foreign Minister Fu Ying, leaving media representatives to have to choose between the two.
Mr Key said he expected to discuss Afghanistan with Mrs Clinton.
New Zealand and Australia have lost soldiers in Afghanistan in the past few weeks. New Zealand is expected to withdraw its troops next April.
Mr Key also expects to touch on climate change with Mrs Clinton, and get her take on global hotspots.
Mrs Clinton's visit is seen as an attempt by the US to recoup some lost ground from China, which has ramped up its involvement in the Pacific.
Although the US has put a stronger focus on the Asia-Pacific region under President Barack Obama, much of that focus has so far gone on Asia.
Mrs Clinton is expected to reinforce the long US involvement in the region and announce new aid initiatives covering health, conservation and illegal fishing.
Washington wants better co-ordination of regional aid and stresses the need to work with other countries to ensure aid is effective.
Mrs Clinton will be part of post-forum talks for the so-called "dialogue partners" - non-member countries with an interest in the region.
China is another of those countries - and although it was possibly inadvertent, the timing of Mrs Clinton's arrival caused competition between the two big powers: it coincided with a press conference by China's Vice-Foreign Minister Fu Ying, leaving media representatives to have to choose between the two.