Dr Francesca Cavallaro, from the Health Foundation, said: "The government has clearly made progress in reducing waiting times, but on current trends our analysis shows that the NHS would just fall short of meeting the 18-week standard by the end of the parliament.
"The scale of the challenge remains significant and even getting close to meeting the target would be a considerable achievement.
"But placing so much emphasis on the 18-week target risks slower progress on other key issues, such as improving access to GPs, which we know is the public's top priority for the NHS."
A Department of Health and Social Care spokesman said a lot of progress was being made and productivity in the health service was improving.
He said the extra money being invested in the NHS, which was introducing modern technology and leading to more evening and weekend working, would help accelerate progress.
But he acknowledged strikes had caused problems.
"We urge the BMA to work with us, not against us, as we drive down the longest waits and get the NHS back on track."
Tim Mitchell, president of the Royal College of Surgeons of England, said: "This analysis otherwise confirms what surgeons see every day - the NHS is still struggling to meet demand, and unless surgical capacity expands, the government will almost certainly fall short of its target."