Lewis will lead the Welsh delegation at a showdown meeting in Heathrow Airport on Friday at which the whole future of the professional club game in three Celtic nations will be on the line.
When the countries last met in May it ended in acrimony with the Scots and Irish throwing Wales out of the tournament and agreeing to play among themselves next season. They were unhappy at the way Wales had successfully negotiated a deal with the RFU to take part in an Anglo-Welsh Cup competition over the next four years.
The argument from the Scots and Irish was that Wales had not been "open and honest" with them about their dealings with England, that by taking part in the tournament Wales were undermining the integrity of the Celtic League and that the five dates required simply could not be fitted into the calendar.
But in a "clear-the-air" memo to the Scottish and Irish Unions, as well as the Celtic League broadcast partners, Lewis has moved to set the record straight on a number of those issues ahead of Friday's meeting. And the WRU Chief Executive remains convinced there is enough flexibility within the season to ensure that the Welsh regions neither compromise the integrity of the Celtic League, nor put unfair pressure on their rivals through fixture compensation.
"The first principle is that the WRU and its four regions are totally committed to the Celtic League. It is our bread and butter, our main ranking tournament for European competition," said Lewis. "Ever since the WRU moved to bring the Scottish teams into the Welsh/Scottish League, and then backed the addition of the Irish to make it a proper Celtic League, we have given our utmost support to the tournament.
"We believe that the format of the last two seasons, where there are 20 fixtures on a home and away basis, is near perfect to meet the needs of everyone in the three nations.
"However, in the early part of this year we were faced with the prospect of being dragged into a 'Rainbow Cup' involving South African provinces, and then excluded from meetings that tried to get four Italian teams into a re-shaped Celtic League played on a home or away basis.
"Against such a background of uncertainty we had to find ways of increasing and improving the fixture lists for our regions - for the good of their players and their fans. That's why, having initially rejected an offer from the RFU and their Premier Division clubs, to play in an Anglo-Welsh Cup we were forced to re-open negotiations with them.
"What has come out of those negotiations is a four-year deal to play in a cross-border cup competition with England's top dozen clubs that will require five weekends in the season - three for Pool matches and two for semi-finals and a final.
"The Scots and the Irish say they cannot find a way to accommodate those five weekends. We will be presenting them with further plans that should allow them to find a solution.
"We simply have to find a way through this or we are all going to suffer. Our broadcasters will leave us, sponsors will walk away and the fans simply won't have the same level of rugby to watch.
"We believe we have found more than one way for the Celtic league season to support our plan to play in the Anglo-Welsh Cup. If the Scots and Irish turn down those plans then they will simply be cutting their own throats along with ours."
The Half a Game initiative is currently sweeping across Wales and proving a major success. The scheme aims to give every young player at least half a game every weekend. WRU TV recently visited a festival in Narberth where clubs have fully embraced the initiative.
Both Bargoed and Swansea were seeking their first win of the Principality Premiership season this afternoon. It proved a fruitful day for the hosts - not only did they win, but Bargoed claimed a try bonus point.
Cardiff managed to keep their unbeaten record at home intact, but only just as Bridgend made them work extremely hard before the Blue and Blacks secured a hard fought Principality Premiership win at the BT Sport Arms Park last night.
Former Wales back row Andy Powell gives a guided tour of The Wern, home of Merthyr RFC, who are determined to prove a lot of people wrong and make their mark in their first season in the Principality Premiership.
Wales Sevens head coach Gareth Williams looks back on the Rio Sevens success where he helped GB win silver. He believes the successful campaign is a huge boost to his Welsh squad as they prepare for another World Series, as WRU TV's Graeme Gillespie discovers
British and Irish Lions head coach Warren Gatland will be heading back home to take on the All Blacks next year where for him, success for 2017 is all about going to New Zealand and winning a Test Series.
Last week all roads led to Eugene Cross Park where defending champions Ebbw Vale hosted this season's launch of the Principality Premiership. WRU TV's Graeme Gillespie was there to capture the thoughts of Damien Hudd, captain of Ebbw Vale, and WRU Head of Performance, Geraint John.
Llandovery made it three in a row when they defeated Aberavon in the final of the National Foster's 7s at BT Sport Cardiff Arms Park on Sunday. On another eventful day of sevens, Newport claimed the Plate and the Dragons won the women's crown
Last week saw Cardiff welcome players from around the world for the 21st Golden Oldies Festival. The tournament features players over 35 years of age, and this year's event saw a select few represent the WRU in a 'friendly' against the Wooden Spoon.
Wales Under 18 captain Callum Bradbury is delighted to have seen his side claim a narrow 18-17 victory against a strong SA Schools 'A' side to end the three-match Under 19 International Series in South Africa on a high note.