WASHINGTON (AP) - President Barack Obama waded into British politics Monday, suggesting that the United Kingdom seek to reform its relationship with the European Union before it decides to simply break away from it. The stance put Obama squarely on the side of British Prime Minister David Cameron, who was visiting the United States as he faces growing pressure at home to abandon the European bloc. The two leaders also displayed a unified front on Syria, with both expressing hope that Russia could be a significant player in bringing about a political resolution to the bloody civil war. The question of the United Kingdom's role in the European Union has been dogging Cameron and even dividing members of his own Conservative Party. From Obama's standpoint, Britain provides the U.S. with an important ally in the EU. Cameron says he wants to work to change and improve the relationship between Britain and the European Union and has promised to hold a referendum on EU participation in 2017. He said submitting the question to a referendum now would "be a false choice between the status quo and leaving." Obama then offered his support. "David's basic point - that you probably want to see if you can fix what's broken in a very important relationship before you break it off - makes some sense to me, and I know that David's been very active in seeking some reforms internal to the EU," Obama said as Cameron shared the podium with him during a brief White House news conference. So long as we haven't yet evaluated how successful those reforms will be, you know, I, at least, would be interested in seeing whether or not those are successful before rendering a final judgment. Obama said the U.K.'s participation in the EU demonstrates its influence, but he acknowledged that making internal changes to the European bloc require tough negotiations involving a number of countries. Both men expressed hope that the United States and the European Union could launch the start of negotiations on a broad U.S.-EU trade deal by next month's economic summit in Northern Ireland. Cameron said that for Britain alone, such a large deal could be worth up to $15 billion a year. "If Britain was outside the EU when the U.S. and the EU agree to an open trade deal, I think that would clearly not be in Britain's interest," said Rob Shapiro, a former undersecretary of Commerce and economic adviser to former President Bill Clinton. Still, Shapiro added, "Let's recognize that we are a long way from a U.S.-EU open trade deal. We're at the beginning of that process. In addition to their shared ground on the European Union and on the desire for a trans-Atlantic trade deal, Obama and Cameron also were of one voice on their approach to Syria, with both taking note of the role that could be played by Russian President Vladimir Putin, a supporter of the regime of Bashar Assad. The U.S. and Russia agreed last week to arrange an international conference to bring representatives of Assad's government and the opposition to the negotiating table. State Department spokeswoman Jen Psaki said the date for a planned Syrian peace conference may slip until June, while the U.S., Russia and others coordinate on getting the rebels and the Syrian government to the negotiating table. Diplomats must also decide whether or not to invite Iran, the Assad regime's top military backer, which Psaki would not rule in or rule out. Cameron and Obama have consistently said that Assad's regime is illegitimate and that he should step down. Cameron conceded that Putin has a different view. "But where there is a common interest is that it is in both our interests that at the end of this, there is a stable, democratic Syria; that there is a stable neighborhood; and that we don't encourage the growth of violent extremism," he said. Obama added: "Our basic argument is that as a leader on the world stage, Russia has an interest as well as an obligation to try to resolve this issue in a way that can lead to the kind of outcome that we'd all like to see over the long term." Associated Press writer Bradley Klapper contributed to this report.