President Bush plans to announce today that he will steer $674 million in additional U.S. humanitarian relief to Africa, a move timed as a gesture to British Prime Minister Tony Blair, his close ally, who has unsuccessfully pushed the president to embrace a far more expansive African aid package.

A top White House official said last night that Bush will unveil the new spending at a joint news conference with Blair, who will be making his first visit to Washington since British elections slashed his parliamentary margin by more than half, a consequence in part of his support for the U.S.-led war in Iraq.

"We cannot ignore these urgent humanitarian needs," said the official, who spoke on the condition of anonymity because the announcement had not been formally made.

But if Blair hoped for a greater payback, Bush has indicated that he will not go along. Blair has been trying to round up international support for a broad, long-term plan to double foreign aid to Africa and forgive 100 percent of African international debt, what some in London call a modern Marshall Plan for the continent. Blair hopes to persuade the world's leading industrial powers to sign off on such a vision in time for the Group of Eight summit he will host in Scotland next month.

Bush, however, has been cool to the notion. Administration officials argue that the United States has tripled aid to Africa in the past four years and that pumping additional billions into the continent right away would not necessarily ensure that the funds were used for intended purposes.

Last week, Bush rejected the financing plan envisioned by Blair and Gordon Brown, chancellor of the exchequer, to issue bonds on world capital markets to come up with the $25 billion extra needed each year in the near term and $50 billion annually by 2015. "It doesn't fit our budgetary process," because it would illegally bind future governments, Bush told reporters who asked about it.

The money that Bush will announce with Blair will be targeted at famine relief in Ethiopia, Eritrea and other African countries and will be enough to feed 14 million people, the White House official said.

The $674 million in U.S. funds will come from an Agriculture Department food reserve program and from money provided by a recent supplemental appropriations bill to fund ongoing military operations in Iraq and Afghanistan, the official said. It comes on top of $1.4 billion already pledged by the United States in the current fiscal year, through the United Nations and nongovernmental organizations, the official said.

"Every additional dollar for Africa is welcome and needed," said Seth Amgott, spokesman for a debt-relief advocacy group founded by the singer Bono. "This announcement falls well short of a comprehensive debt cancellation, increased international assistance and trade reform package to get Africa out of the cycle of famine and disease."

Blair, who also plans to meet with French President Jacques Chirac, German Chancellor Gerhard Schroeder and Russian President Vladimir Putin before the G-8 summit, has proposed that the world's richest powers increase their foreign aid to 0.7 percent of national income. The current average is barely a third of that, and the United States provides proportionately less.

Bush has tried to target aid to Africa and other impoverished regions through Millennium Challenge Account grants, which direct money only to countries that meet guidelines for promoting democracy, limiting corruption and reforming institutions. The program has certified a handful of countries for receiving aid.