The Democratic Party released a 2012 platform Tuesday that omits previous language describing Jerusalem as the capital of Israel, sparking an unexpected dust-up just as President Barack Obama is preparing to accept his party's nomination for a second term.

The platform isn't binding on a president, and the document stresses that Mr. Obama and the Democrats "maintain an unshakable commitment to Israel's security." But the issue underlines a continuing challenge for Mr. Obama as some critics have persistently questioned his support for Israel, even while he insists it is strong.

Though Israel considers Jerusalem its capital, the U.S. has long regarded it as a city whose status should be the subject of international negotiations including the Palestinians and has maintained its embassy in Tel Aviv.

Republicans wasted little time seizing on the issue, hoping to peel away from Mr. Obama at least a few Jewish voters, a traditionally Democratic group, particularly in states such as Florida. The presidential election is shaping up as a potentially razor-thin contest, where even small shifts of voters in key states could make the difference.

Party platforms often receive little attention, since their details can be and often are ignored by the candidates. But this year they are generating more controversy, with Democrats criticizing the Republican platform for omitting any exceptions to its opposition to abortion and supporting English as America's official language, and the GOP now seeking to challenge Mr. Obama's backing for a longtime ally.

In 2008, the Democratic platform declared that "Jerusalem is and will remain the capital of Israel." It added, "The parties have agreed that Jerusalem is a matter for final status negotiations." The platforms of both parties have consistently included similar language.

This year, the Democratic document omits any mention of Jerusalem's status, even while seeking to emphasize Mr. Obama's friendship with Israel with such statements as "any Palestinian partner must recognize Israel's right to exist, reject violence, and adhere to existing agreements."

GOP nominee Mitt Romney issued a written statement saying, "It is unfortunate that the entire Democratic Party has embraced President Obama's shameful refusal to acknowledge that Jerusalem is Israel's capital."

Former Rep. Robert Wexler (D., Fla.), who has acted as a liaison between Mr. Obama and the Jewish community, defended the president from the convention podium Tuesday night.

"Over the past four years, the president has proven this commitment time and again in both word and deed," Mr. Wexler said.

Mr. Obama has had a shaky relationship with Israel and its hawkish prime minister, Benjamin Netanyahu. In 2011, Mr. Netanyahu delivered a rare public rebuke of Mr. Obama at the White House over the president's comments that peace negotiations should resume based on Israel's borders before it gained new territory in the 1967 Six Day War.

The omission of Jerusalem in the Democratic platform received prominent attention from Israeli websites, which also noted the document's emphasis on American security aid to the Jewish state and the relegation of the mothballed Israeli-Palestinian peace process to secondary treatment.

Democrats said that Mr. Obama's commitment to Israel is solid, pointing to broad increases in security cooperation, and that Republicans were seeking to exploit what is usually a bipartisan allegiance to the Jewish state.

"Nobody can read that platform and come away thinking the president has been anything less than a steadfast supporter of Israel," said Marie Harf, associate policy director for national security of the Obama campaign. "To try to turn that into a wedge issue is not helpful for Israel's security."

Democrats said the White House shares the policy position of previous administrations of both parties that Jerusalem's future is a matter to be negotiated in peace talks between Israel and the Palestinians. They said the language on the platform was designed to parallel that official diplomatic position.

The 2008 platform wasn't drafted by Mr. Obama's team, some Democrats said. Now that he occupies the White House, they feared that any statement in the platform could be read overseas as a shift in policy by a sitting president, making its wording far more sensitive.

"The official position of this administration on Jerusalem is no different than the position of numerous previous administrations of both parties—that it is a final status issue to be negotiated directly by the two parties," said a spokesperson for the Democratic National Committee.

Still, when President George W. Bush was seeking re-election in 2004, the Republican platform stated that "Republicans continue to support moving the U.S. embassy from Tel Aviv to Israel's capital, Jerusalem."

Mr. Bush, though, never moved the embassy. And when Al Gore, then the incumbent Democratic vice president, ran in 2000, the party's platform said "Jerusalem is the capital of Israel."

Presidential candidates regularly promise to move the U.S. embassy from Tel Aviv to Jerusalem, then fail to act on that promise once they reach the White House out of concerns about inflaming Arab sentiment and upsetting the peace process.

Democratic officials also said that the platform language was vetted in public platform hearings in Minneapolis and Detroit within the past few weeks without objections. Jewish groups were in attendance and didn't raise any concerns, they said.

A spokesman for the Israeli embassy declined to comment. Maen Areikat, the main Palestinian representative to the United States, said he couldn't comment on the platform because he hadn't yet read it.

The Republican platform also changed its language regarding Jerusalem since 2008. The earlier version called for moving the American embassy to Jerusalem; the 2012 document reiterates that Jerusalem is Israel's capital, but doesn't urge moving the embassy.

The issue of Jerusalem's future has been a sensitive one for U.S.

policy makers since Israel's creation in 1948. (The city was divided by the armistice lines drawn after the 1948 fight, and Israel declared it the Israeli capital in 1950.) Many American Jews see Jerusalem as Israel's biblical capital. At the same time, Arabs have called for Jerusalem also to be capital of a Palestinian state.

Congress passed a measure in 1995 saying the U.S. embassy in Israel must be moved to Jerusalem, but allows presidents to waive the requirement.

Mr. Romney clashed with the Obama administration on the status of Jerusalem just weeks ago. During a trip to Israel in July, Mr. Romney angered Palestinians and others by saying in an address, "It is a deeply moving experience to be in Jerusalem, the capital of Israel."

The White House disavowed his comments, noting that successive U.S.

administrations have taken the view that the status of Jerusalem would have to be settled through negotiations between Palestinians and Israelis.

The omission of Jerusalem in the Democratic platform received prominent attention from Israeli websites, which also noted the document's emphasis on American security aid to the Jewish state and the relegation of the mothballed Israeli-Palestinian peace process to secondary treatment.

Palestinians are unlikely to interpret the new plank as reflecting a shift by the administration to a policy more in their favor, in part because there is no mention of Jerusalem as the capital of a future Palestinian state.

Mitchell Barak, an Israeli pollster and former aide to Prime Minister Netanyahu, said, "Jerusalem is not a serious election issue, because no president is changing the status of Jerusalem without negotiations and some kind of agreement."