"But we are making serious progress. Since 1939 we've been talking about a free trade agreement. It is 2019, and you have to say to yourself 'what happened on the way through?'
Whatever happened that is a roadblock to where we are going, we have to get past it, and we are going to get to where we want to go, which is the announcement of the opening of free trade talks with the United States."
His most recent trip followed two previous trips to Washington by Peters, in December and July, in a bid to persuade the US of the economic and geo-political strategic value of a trade deal.
Prime Minister Jacinda Ardern's first meeting with US President Donald Trump was in New York in September, after which Ardern said Trump was very positive about the prospects of a deal.
The US representative at the meeting of the G20 Foreign Ministers is Deputy Secretary of State John Sullivan as rumours circle that Pompeo could leave the role to stand for Senate in Kansas.
Peters said he did not know what Pompeo intended to do, but did not expect a change in personnel in that role to derail New Zealand's efforts on trade.
"We've come from Rex Tillerson to Mike Pompeo in almost a seamless way, and we've got the attention of the Administration so to speak."
Like Japan, New Zealand has been left to focus on trying to get a bilateral deal with the US after it withdrew from the TPP talks - one of Donald Trump's very first moves after becoming US President.
Japan recently inked theirs, but it was not an easy road - Japan had to exclude its most lucrative export - motor vehicles - from the deal.
One expert spoken to by the Herald in Japan said it could not refuse to sign the deal because the US had threatened to boost tariffs on motor cars even higher if it did not go ahead with it.
Peters would not discuss whether New Zealand would be concerned about similar treatment from the US around agriculture.
"In our case we are on the other side of the door with our nose hard against the window. We are not in the same situation Japan was."
He said the first goal was prising open the door to those negotiations. "Once we've got the door open, the conversations start."
Peters at the G20
Peters spoke on Saturday at a session on increasing trade tensions and the need to reform the WTO, which has been unable to appoint to its disputes settlement board because of the US blocking candidates.
"We want world trade to be free and fair, and if there are departures from the rules, some place where we have an international umpire to straighten the circumstances out."
Peters was invited to attend the G20 meeting by the Japan Government which is hosting it.
On his way over, he had tweeted that he was going to "try to sort out the world".
Asked how he would do that, Peters said he would "bring a New Zealand perspective as a country that has got what you might call economic and social and security skin in the game, but is not here with a bias or prejudice unhelpful to the countries we are talking to."
Despite the agenda's focus on trade and the Sustainable Development Goals, much of the focus has been on the tension between Japan and South Korea. At the last minute, South Korea pulled back on its threats to step out of an intelligence sharing arrangement with Japan.
Peters said New Zealand had strong relations with both countries, and implored them to sort it out. "These sorts of contretemps just cannot be afforded."
On the first day, Peters also had meetings with Indonesia's foreign minister, Marsudi Retno, and Saudi Arabia's Prince Faisal bin Farhan Al Saud, who Peters had also met when he travelled to Turkey after the Christchurch mosque attacks to speak to Muslim leaders.
He expected to catch up with several other ministers informally, including Australia's Marise Payne.
He also sat next to Federica Mogherini, the EU's foreign affairs representative, at the formal dinner. He had said he would emphasise New Zealand's desire to wrap up trade talks with the EU.
The Foreign Ministers feasted on local delicacies, such as blue crab, steamed abalone (paua), wild boar cutlets, and boiled chrysanthemum.
The toasts and drinks were three types of sake.
*Claire Trevett is in Japan as part of a journalists' programme funded and organised by Japan's Ministry of Foreign Affairs.