As the American-Israel Public Affairs Committee’s super-sized annual conference fills out the Washington Convention Center this week, it is easy to assume that AIPAC is the only pro-Israel advocacy groups in town.

But Washington, D.C., is actually home to a handful of pro-Israel organizations on the left and the right, each with its own objectives.

To be sure, groups such as Americans for Peace Now, the Israel Policy Forum and the Zionist Organization of America aren’t about to overtake an organization that is perennially ranked as one of the most powerful lobbying organizations in Washington and which lined up 99 lobbying appointments in the Senate and 350 in the House on Wednesday alone.

The group’s clout is not expected to be curbed, even after scrutiny of AIPAC officials in a still-unfolding FBI investigation into allegations of classified information being passed from the United States to Israel. (An AIPAC spokesman declined to comment on the investigation, but a source close to AIPAC said that the government has told the organization that neither AIPAC nor any of its current employees is the focus of the investigation.)

Indeed, on Monday night, nearly 5,000 supporters — including roughly half of Congress as well as representatives from 49 different countries — turned out for AIPAC’s annual conference banquet. Senate Majority Leader Bill Frist (R-Tenn.), Senate Minority Leader Harry Reid (D-Nev.), Speaker Dennis Hastert (R-Ill.) and House Minority Leader Nancy Pelosi (D-Calif.) took to the podium to pledge their continued support for Israel.

Still, AIPAC’s stance — to strongly support the government of Israel, which in recent years has meant taking a relatively hawkish line on foreign affairs — has left niches for other groups to fill on both ends of the ideological spectrum.

Americans for Peace Now, founded in 1981, is the sister organization of Peace Now, its Israeli-based counterpart. It has a database of some 25,000 supporters.

“We are a Jewish-Zionist organization that works to enhance Israel’s security through peace,” said Lewis Roth, APN’s assistant executive director for public affairs.

APN’s policy objectives tend be somewhat narrower than AIPAC’s, focusing exclusively on the peace process between Israel and its neighbors, Roth said. Moreover, the organization’s objective of finding a peaceful solution to Middle East strife remains consistent, regardless of which party leads the Israeli government, Roth said.

“A lot of positions we’ve adopted — for example, the two-state solution and the need to evacuate the settlements [in Gaza] — have been adopted by a majority of the people in Israel and the American Jewish community,” Roth said.

APN uses its limited resources effectively, said Jeremy Rabinovitz, chief of staff for Rep. Lois Capps (D-Calif.). “Although they don’t have a huge budget or a phalanx of lobbyists, APN’s Washington operation is second to none,” Rabinovitz said.

In the meantime, the Israel Policy Forum, based in New York, focuses on encouraging the U.S. president to become personally involved in Mideast diplomacy, with the goal of achieving a final status agreement in the Israeli-Palestinian conflict. The organization has some 17,000 supporters.

The focus on U.S. involvement in the peace process is the main policy difference between IPF and AIPAC, said M.J. Rosenberg, IPF’s director of policy analysis.

“We don’t believe that peace in the Middle East can be achieved unless the president of the U.S. is involved,” he said.

Although IPF doesn’t have a formal lobby, IPF asserts its influence through publications. Rosenberg’s weekly column, “IPF Friday,” is published on the organization’s Web site and e-mailed to a list of some 10,000 people, including Members of Congress and diplomats from all over the world.

The column is regularly reprinted in publications throughout the world, such as The Jerusalem Post and The Beirut Daily-Star, Rosenberg said. And Laura Capps, a spokeswoman for Sen. Edward Kennedy (D-Mass.), said Rosenberg’s column is widely circulated in Congress.

“He’s an important voice on critical issues,” she said.

Other left-leaning pro-Israeli advocacy groups with influence inside the Beltway include the Religious Action Center of Reform Judaism, which is the Washington office of the Union for Reform Judaism, and Chicago-based Brit Tzedek v’ Shalom, a grass-roots organization with 30 chapters across the United States.

Still, such organizations are dwarfed by AIPAC. Comparing such smaller pro-Israel interest groups is like comparing a fly to a lion, says one AIPAC supporter.

On the other side of the political spectrum, the conservative Zionist Organization of America is working to influence lawmakers in support of its agenda.

The New York-based ZOA is the oldest pro-Israel organization in America and boasts some 40,000 members. Only AIPAC has more paid lobbyists.

ZOA’s agenda is distinct from that of AIPAC in several ways, said Morton Klein, the national president of the ZOA.

ZOA opposes any funds going to Palestinian Arabs until all obligations outlined in the roadmap for peace are fulfilled. Additionally, ZOA opposes the pullout of Israeli settlers from Gaza — a plan pushed despite settler resistance by Israeli Prime Minister Ariel Sharon — and refuses to support the establishment of a Palestinian state.

“We’re against the establishment of a Palestinian state because it will become just another terror state in the region,” Klein said. “We should be ending terror states, not creating them.”

ZOA’s conference in December drew roughly 1,000 people, said Klein. Sen. Sam Brownback (R-Kan.) spoke at the conference.

“The ZOA has been a proactive voice for members of the American-Jewish community who have an interest in the security of Israel for well over 100 years,” said Rep. Jim Saxton (R-N.J.) through a spokesman. “During my tenure as a Member of Congress, the ZOA has worked hard to strengthen American-Israeli relations through support for legislation on Capitol Hill educational activities and public affairs programs.”