Khan has taken 121 Test wickets

Left-arm seamer Bracken has been a regular for Australia over the last six months and said he may not be able to play for most of the English season.

Zaheer, 27, has played 42 Tests and 107 one-day internationals.

But he is not currently a regular for India, despite enjoying a fine season in domestic cricket.

"To have the opportunity to play for Worcestershire is a privilege," said Zaheer.

Zaheer has had an outstanding domestic season and will bring variation to our bowling attack Worcestershire director of cricket Steve Rhodes

"I very much look forward to the season ahead and re-establishing myself on the international scene whilst helping the county to win as many matches as possible."

Worcestershire's director of cricket Steve Rhodes was delighted to snap up an experienced international at such short notice.

"We're pleased for Nathan that he had such a successful six months since we signed him but we really want stability with our overseas players this year," said Rhodes.

"We targeted a left-arm fast bowler from the start of our deliberations for 2006. Zaheer has had an outstanding domestic season in India and will bring variation to our bowling attack."