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By Matt Spetalnick

WASHINGTON, Sept 9 (Reuters) - The number of U.S. allies involved in the Iraq war will be reduced to just a "handful" before the end of the year, a senior Bush administration official said on Tuesday.

The official briefed reporters shortly after President George W. Bush formally presented a plan to cut U.S. force levels in Iraq only modestly over the rest of his term, pulling 8,000 troops out by February and deferring further decisions about withdrawals to his successor.

"Just as we're reshaping U.S. force structure, we're going to reshape the coalition," the official said. "We'll go from about 29 countries to a handful of countries in the course of the next 90 days or so."

Bush, an unpopular president waging an unpopular war, said the troop drawdown was made possible by a recent dramatic drop in violence in Iraq but made clear his concern that any deeper troop cuts now could jeopardize those security gains.

"The same 'return on success' logic will be applied in the coming months to the coalition," the official said. "Some of these contingents are rather small -- tens of soldiers -- and some are as big as the British contingent."

The official declined to name the countries that would be pulling out.

"The reason is that we want the government of Iraq to issue these invitations formally on a bilateral basis to this handful of countries," the official said. "So we don't want to get out in front of the government of Iraq there."

The United States has 146,000 troops in Iraq, the largest of any foreign country. Britain is second with 4,100 troops and all other countries in the coalition have fewer than 1,000 troops there, down to Singapore with one.

Washington is negotiating a long-term security deal with Prime Minister Nuri al-Maliki's government that would govern the presence of U.S. forces in Iraq after a United Nations mandate expires at year's end.

Maliki, emboldened by the recent successes of Iraq forces, is looking for assurances that U.S. troops would not remain indefinitely, although the Bush administration has long resisted setting a firm timeline for withdrawal.

Bush, in a speech on Iraq, took note of Australia's withdrawal of its combat forces and Poland's plan to do the same, saying: "Many more coalition nations will be able to conclude their deployments to Iraq this year."

Britain has already substantially reduced its force. Other European countries faced with strong anti-war sentiment at home have come under pressure to wrap up their involvement in Iraq. (Reporting by Matt Spetalnick; Editing by Kristin Roberts and John O'Callaghan)

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