European rugby chiefs say they are adopting a "logical position" with regard to global fixture calendar negotiations that could see changes in domestic and European schedules from 2019.
European Professional Club Rugby, organisers of the European Champions Cup and Challenge Cup competitions, are keen to see pool games played in one extended block throughout December and January, as opposed to three current two-week groupings in October, December and January that are separated by Aviva Premiership fixtures and autumn Tests.
The European quarter-finals, currently staged in late March or early April, would be brought forward to January before the Six Nations, offering a much longer period to market and sell tickets for the European semi-finals and finals in late April and May.
Any European fixture restructuring would mean changes to the Premiership and Guinness PRO12 calendars, with, it is understood, potentially an October start, rather than the current early September kick-off.
"It's not just a question of the European tournaments, which are a key part of the northern hemisphere season and that's not going anywhere - we have six more years on the current agreement for our competition with the leagues and the unions - but it's also about the global game," EPCR chairman Simon Halliday told Press Association Sport.
"What everyone is looking for is for longer bursts of activity in their competitions, whether that is in Europe, domestic leagues, the autumn internationals, Six Nations and so on.
"For us, the semi-finals of the Champions Cup are among the key dates in the rugby calendar, and we owe it to ourselves to get the best position to market those matches in a way that fills up the stadiums and takes the rugby to the greatest possible crowd.
"This is a premium competition, and we have a responsibility to our stakeholders and to rugby as a whole, to do the best we can to maximise the potential that it has, both in sporting and financial terms, so this is a logical position to take and it's something that we are in ongoing discussions about with our stakeholders."
A new rugby union global calendar is set to take effect from 2019.