Come April 15, tax day, Josh Ruebner plans to send his group's members to post offices, dozens of them across the country, to "educate" people mailing in their tax forms that the United States should end military aid to Israel.

The activists will hand out literature noting that the $2.8 billion Israel gets each year could fund 65,000 vouchers for low-cost US housing or retrain half a million Americans for green jobs. It costs each taxpayer $19 a year, says Mr. Ruebner, national advocacy director of the US Campaign to End the Israeli Occupation, which aims to get Israel out of the West Bank, East Jerusalem, and Gaza.

One way to accomplish that, he figures, is to threaten a cutoff of US aid.

He faces formidable obstacles. The US has already promised Israel $30 billion of military aid from 2009 through 2018. Given the power of the Israeli lobby and widespread public support for Israel in its conflict with the Palestinians, neither Congress nor the Obama administration is likely to directly cut that aid money. It would be too risky politically.

But the administration's recent quarrel with Israel over its plans to build more housing in Jerusalem, seen as an impediment to peace talks, has raised the profile of US-Israel relations – and, by extension, US aid to Israel.

Is it too much? Since 1949, the US has given Israel more than $101 billion in aid, including $53 billion in military help, $31 billion in economic aid, and $15 billion in other grants, a 2008 Congressional Research Service study found.

Israel is a relatively rich country, with a standard of living similar to Spain. Yet the US aid it gets is a bit more than the $2.6 billion going to impoverished Afghanistan, which America is eager to develop. It's far more than what goes to the next largest aid recipients – Egypt, Pakistan, and Jordan.

In 2007, President Bush phased out economic aid to Israel in favor of a boost in military aid, but that amounted to a 25 percent overall hike in funds. Furthermore, a reduction in the cost of maintaining Israel's expensive armed forces frees up government money to spend on other programs, including subsidized housing in the occupied territories.

Legally, US loan guarantees of up to $10 billion to Israel can't be used to finance Israeli settlement building there. In the mid-1990s and again in 2003, the US did shrink those guarantees a bit because of settlement building, presumably raising Israel's cost of borrowing.

To Eugene Bird, president of the Council for the National Interest, a group advocating a "more balanced" approach to Middle East affairs, US money does in effect finance settlements in the West Bank that house 400,000 settlers – "though I never will be able to prove it," he confesses.

So if President Obama wants to pressure Israel to stop expanding settlements, what can he do?

He should not engage in a public fight, says Stephen Walt, a Harvard University professor of international relations and coauthor of a book on the Israel lobby. Rather, he says, Mr. Obama should use the bully pulpit to express displeasure, maybe calling the settlements "illegal." He should take diplomatic steps, such as voting for a United Nations resolution condemning the 42-year-old occupation; slow down or trim US purchases of Israeli military products (worth perhaps half a billion dollars a year); and limit loan guarantees.

One advantage of these measures: Congress would not need to be involved, notes Mr. Walt.