British Olympic 400m champion Christine Ohuruogu and US world title holder Sanya Richards-Ross will renew their rivalry in two UK races this summer.
The pair have nine major gold medals between them but didn't face each other in 2010 due to injuries.
Birmingham's Alexander Stadium hosts the first race on 10 July.
They will then meet again at the London Grand Prix at Crystal Palace (5-6 August), the last major event before the World Championships in South Korea.
Ohuruogu expects the competition in a World Championship year to be tough, and said: "The 400m was a bit of a weird event last year, with both myself and Sanya out for a majority of the season, and only four girls breaking 50 seconds.
"However, the most exciting thing was that 10 girls were within a second of each other and every race was very close.
"I expect it to be similar this year but everyone will be pushing that bit harder to get ready for the World Championships. At the moment, I'm just making sure I'm in the best possible shape as we get towards Daegu." she added.
The two athletes first met each other at the Crystal Palace National Sports Centre back in 2005, for Ohuruogu says both races will be special: "I have fond memories of both the Alexander Stadium and Crystal Palace, plus I love running in front of my friends and family."
She continued: "Since winning the World Champs in 2007 and Olympic Games in 2008 I always get a great reception in the British meets and look forward to the same in 2011. "
Richards-Ross is also trying to put a disappointing 2010 behind her but is relishing the prospect of renewing her rivalry with Ohuruogu.
She said: "Christine and I have met quite a few times but it's been a while since we raced in the UK, and now the fans have the chance to see it happen twice."
The American is also on her way back from a disappointing 2010 and has no concerns about facing Ohuruogu on home soil.
She added: "I am happy to be back on the track. My first couple of races have gone pretty well. I feel it will take me a few more to get back to where I want to be but I am looking forward to it.
"With Allyson Felix attempting the 200/400m double, Shericka Williams and Christine Ohuruogu, hopefully healthy, the fans are in for some fast times and fierce battles in the 400m this year."