Public anxiety over mounting casualties in Iraq and doubts about the long-term consequences of the war continue to rise in the United States and have helped erase President George W Bush's advantage over John Kerry on dealing with terrorist threats, a poll has indicated.

Only half the country now approves of the way Bush is managing the US war on terrorism, down 13 points since April, according to the Washington Post-ABC poll.

Barely two months ago, Bush comfortably led Kerry by 21 percentage points.

Today, 48 per cent prefer Kerry with only 47 per cent leaning towards Bush.

With less than 10 days to go before the US turns over power to a new government in Iraq, the poll shows that Americans are considering the costs and benefits of the war on terror. Campaign advisers to both Bush and Kerry believe voters' conclusions about the president and Iraq will play a decisive role in determining the outcome of the November election.

The shift away from Bush is potentially significant because Bush has consistently scored higher on fighting terrorism than on Iraq. If the decline signals a permanent loss of confidence in his handling of the campaign against terrorism, that could undermine a central part of Bush's reel election campaign message, the Washington Post said.