Last week, speaking at the United Nations, President Barack Obama laid out an ambitious set of goals with regards to the Middle East. In the remainder of his second term, the chief executive promised to intensify efforts to end the civil war in Syria, broker a lasting settlement between the Israelis and the Palestinians, and initiate a dialogue with Iran to end the standoff over its nuclear program. The government shutdown, however, imperils all of these initiatives, by exposing the President's political weakness vis-a-vis the Congress.

The failure to get even a short-term continuing resolution through the Congress—leaving aside the point that the United States has not had actual budgets passed for years—sends a clear signal that partisan politics trumps even matters of the highest national interest. But it also communicates to other countries that if the U.S. government is so dysfunctional that it cannot get a basic measure for simply funding government operations through the legislature, how in the world is President Obama going to shepherd the legislation that would be required for the United States to be able to move forward on the president's Middle East agenda?

For the reality is that despite the vast powers that presidents have claimed to possess in conducting the foreign affairs of the country, there is no bypassing Congress when it comes to key authorities—not to mention new budget outlays—that would be needed for Obama to make any progress on the matters he highlighted in his UN General Assembly address.

Take Iran. Obama's freedom of maneuver vis-a-vis Tehran is highly circumscribed by existing Congressional mandates. Unlike his predecessor Bill Clinton, who, in the course of normalizing relations with Vietnam during the 1990s, was able to use his executive authority to lift sanctions and rescind other restrictions against Hanoi, Obama can take no such steps if President Hassan Rouhani is prepared to make significant gestures to alleviate the international community's concerns about Iran's nuclear program. Even when it comes to permitting other allies and partners to respond positively to any Iranian overtures—for instance by allowing countries to increase their purchases of Iranian oil—Obama's hands are tied by legislation that requires him to pressure other countries continuing to do business with Tehran.

Rouhani's entire diplomatic outreach to the West—one which is not supported by the more radical factions within the Iranian regime—is predicated on the assumption that a more accommodating Iran could obtain relief from the punishing sanctions which have done real damage to the Iranian economy. But Obama will need Congress to roll back or suspend some of its provisions should he choose to respond. But as with the continuing resolution, opponents of the president will not have to do anything to derail engagement. Simply by doing nothing, Congressional skeptics of Rouhani's good faith can prevent Obama from being able to offer reciprocity. If, as some experts have concluded, Iran's new president only has a temporary window in which he can pursue diplomacy—before hardliners around the Supreme Leader conclude that such efforts are fruitless—a possible "reset" with Iran could wither on the vine of Congressional inaction.

On Syria, by making the choice that any military strike on Damascus would require Congressional approval, the president turned over his freedom of action to Capitol Hill. If the agreement on Syrian chemical weapons hammered out in Geneva between Secretary of State John Kerry and Russian foreign minister Sergei Lavrov, and then enshrined in a UN Security Council resolution, proves to be unworkable, Obama returns to square one in trying to convince a still largely skeptical Congress to support a vague, limited military action against Syria—and opposition to this is one of the few issues that truly enjoys bipartisan support. At the same time, the sense that the Obama administration has ceded the initiative to Moscow—a point discussed at length by my colleagues John Schindler and Tom Nichols in these pages—has increased skepticism on the Hill that the Obama team has a coherent, workable approach to Syria that safeguards fundamental U.S. interests in the region. Congress is unlikely to grant the president any broad-ranging authorization to use military force in Syria, and without it, the U.S. must rely solely on the strength of its diplomacy.

Finally, we come to the Israel-Palestine issue. Even before the government shutdown, this was one area where Congress was not inclined to give the president much of a blank check. What pressures can Obama bring to bear on both sides to force progress towards a settlement? Congress is not going to permit the executive branch to use U.S. aid to Israel as a bargaining chip, nor is it inclined to support massive amounts of U.S. assistance as an inducement for Palestinian cooperation. Moreover, a legislature loathe to approve "pinprick" strikes against Syria is not going to commit to deploying American forces to serve as robust peacekeepers to help enforce any final agreement between Israel and an emerging Palestinian state.

It is possible that Obama's address was entirely aspirational. But if it reflects his foreign-policy priorities for the remainder of his second term, then he will have to find a way to work with Congress—and be able to get his agenda passed in terms of concrete legislative proposals. Soaring rhetoric will be insufficient to get the job done.

Nikolas K. Gvosdev, a senior editor at The National Interest, is a professor of national-security studies at the U.S. Naval War College. The views expressed are entirely his own.