Tom James is on course to defend his Olympic title in the men's four after Alex Partridge withdrew from contention and took a place in the men's eight, GB Rowing confirmed.
James has been reunited with fellow 2008 Olympic champions Andrew Triggs Hodge and Pete Reed plus Alex Gregory, with whom he won world championship gold last year, in Britain's flagship boat for the opening World Cup regatta in Belgrade on May 4-6.
The final Olympic selection will be confirmed on June 6 but this choice for Belgrade is a strong pointer to the make-up of the GB Rowing squad for London 2012.
Men's coach Jurgen Grobler had delayed a decision on whether James or Partridge would take the final seat in the four and wanted to run further testing during the current training camp in Varese.
But Partridge, already frustrated by the uncertainty, told Grobler he wanted to focus his training on the boat he would race in at London 2012 and accepted a seat in the powerful men's eight crew.
"I feel like a weight has been lifted off my shoulders and I now know what I am getting on with," Partridge said from Varese. "I had been thinking about it for a while. I was frustrated when the squad was announced because I felt I had done enough to prove I was good enough to be in the four.
"When we got out here and Jurgen said he wanted to do more testing and it would be another week down the line, I said 'I see it differently. I don't want to waste any more time. I want to get on with what I am going to row in for the Olympic Games' and I withdrew myself from the four.
"I think that is where I will get the best out of me for the Olympics."
The men's eight has the potential to top the podium at London 2012, with Partridge joining Ric Egington and Constantine Louloudis in strengthening a boat that won silver at last year's world championships.
Egington has also moved over from the men's four to make way for Reed and Hodge, while James and Gregory continue in the boat that won world championships gold in Bled last autumn.