England's hopes of squaring their Test series against South Africa flickered briefly before heavy rain brought an early end to the fourth day of the second Test at Headingley on Sunday.

A fluent innings of 68 by Matt Prior gave England a six-run first innings lead with the hope of bowling out an injury-hit South African team cheaply in a second innings which started shortly before lunch.

But opening batsmen Graeme Smith and Jacques Rudolph resisted some hostile bowling before a mid-afternoon thunderstorm - the second rain stoppage of the day - ended play with South Africa on 39 for no wicket, a lead of 33.

Smith was one of three of South Africa's regular top four batsmen carrying an injury. He had to be helped off the field on Saturday after falling heavily on his left knee.

But he led his side onto the field with the knee heavily strapped and when he batted he did not appear to be hampered in his running between the wickets.

Rudolph opened the batting with Smith in place of first innings century maker Alviro Petersen, who did not field because of a hamstring injury and will be unable to bat until five wickets have fallen.

South Africa suffered a further injury blow when all-rounder Jacques Kallis could not take the field on Sunday because of back spasms.

South Africa lead the three-match series 1-0 after winning the first Test at the Oval by an innings and 12 runs. They will overtake England at the top of the world Test rankings if they win the series.

Short of a sensational collapse by South Africa on Monday, a draw is probable at Headingley, leaving England needing to win the final Test at Lord's, starting on August 16, to stay at number one.

England were bowled out for 425 shortly before lunch on Sunday. South Africa were five for no wicket in their second innings when lightning and rain drove the players off the field three balls into what would probably have been the last over before lunch.

After a two-hour delay, which included the lunch break, only another hour of play was possible before the players had to leave the field again. Smith and Rudolph batted watchfully against disciplined bowling under a heavily overcast sky before rain swept in again.

England lost top scorer Kevin Pietersen to the second ball of the day when he was trapped leg before wicket by Morne Morkel without adding to his overnight score of 149.

It ended an innings which changed the course of the match after South Africa had seemed in control.

Prior took over the attacking role played by Pietersen on Saturday, cracking eight fours before he was ninth man out, top-edging a sweep against leg-spinner Imran Tahir to deep fine leg.

Tim Bresnan helped Prior add 45 for the seventh wicket before Tahir wrapped up the innings. Tahir took the last three wickets at a cost of nine runs to finish with three for 92.