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Nick Willis, Olympic silver medallist, has not yet qualified for August's world championships - but says it's no time to panic.

Willis has embarked on a month of altitude training in Arizona as he bids to qualify in the 1500 metres for the world track and field championships, starting August 27 in Daegu, South Korea.

His fastest time since the qualification period began on October 1 was at Melbourne in March when he ran 3m 38.76s. He needs to run 3m 38s or better to qualify in the B standard time and 3m 35s to qualify in the A standard for Daegu. He ran 3m 42.38s to claim bronze at October's Commonwealth Games.

The Olympic silver medallist says it is no time to panic. He can still qualify for Daegu right up until August 15.

"I still need the qualifying time to be selected for the world championships but the approach I've always taken is if I'm not good enough to do the time, then I'm not good enough to make the final. If I'm not going to be competitive, I don't want to be there making up the numbers.

"I've attended plenty of those types of events before and, after winning a medal [at Beijing], I know the level I need to meet."

Willis has run the 28th fastest 1500m time this year although 17 of those above him on the list are Kenyans. Only three athletes from each country can compete at the world championships. Twelve athletes (10 Kenyans) have met the A standard and 26 athletes (16 Kenyans) have met the B standard.

Willis has a couple of races in the United States lined up next month and his agent is working on getting four to six races in Europe in July before he rests ahead of the world championships.

The 28-year-old has enjoyed his first injury-free build-up to a northern hemisphere season in three years. It has enabled him to do two months' base training before he headed 2130m above sea level to Flagstaff, Arizona a fortnight ago.

"We're here for exactly one month," Willis says. "The theory is your red blood cell count increases when you get the limited oxygen at altitude so you can then absorb more oxygen into your blood when you return to sea level. This effect doubles from week three to four so, unless you do the full four-week cycle, you're not maximising the effect. After four weeks, it plateaus.

"They say you're supposed to run within 48 hours of coming down from altitude to get the best effects so I'm racing [the mile] at the Prefontaine Classic. It will be an interesting experience, one which I have never had before.

"The past two years I've gone under the knife at the start of April; last year I was able to salvage a season [with the Commonwealth Games so late]. This year there have been no interruptions."

Willis will back up a week later with the Diamond League grand prix meet in New York before heading to Europe. He has entered one of his favourite events at Paris-St Denis - where he beat John Walker's 30-year-old 1500m record of 3m 32.4s in 2005. He eclipsed that new mark by 0.21s with a run of 3m 32.17s at Paris-St Denis the following year.

"The plan is to enjoy a good period of racing without the risk of peaking too early or burning out. My approach in 2008 was to be sparing in my European racing. This time I want to give Europe a good go and will evaluate what works best before we schedule next year for the Olympics." After Europe Willis will spend two to three weeks training back home in Ann Arbor, Michigan. He believes it is safer being around medical staff in case injuries pop up, as well as enjoying the familiarity of home. He plans to acclimatise in Hong Kong again ahead of the world championships in Daegu, as he has done before the Beijing Olympics and Delhi Commonwealth Games.

Team Willis [Nick and wife Sierra] as well as several other athletes who have been training with him since the start of the year have at least found a way to escape the intense preparation. Their Western-themed condominium overlooks the third hole of a local Flagstaff golf course.

That has meant an opportunity to relax from their balcony bar and moonlight as mock commentators from horse-saddle bar stools.