Negotiations culminating in the November 24, 2013 Joint Plan of Action (interim nuclear agreement) signed by the U.S. and the Islamic Republic of Iran were unprecedented in the 35-year history of the two governments’ relations. The Obama and Rouhani administrations continue to navigate a precarious course, however, threatened on their domestic flanks by distrustful hardliners and on their foreign fronts by adversaries and allies alike.

There has never been greater potential for détente between the two nations, which could dramatically realign the geopolitics of the Middle East and generate positive momentum toward resolution of three conflicts in the region—Syria, Iraq, and the Israeli-Palestinian conflict.

On the other hand the interim nuclear agreement, which Iran began implementing on January 20, could be the eye of the storm: a moment of calm before the descent into an increased level of instability provoked by the imposition of additional U.S. sanctions, the fracturing of the international sanctions regime, increased Iranian intransigence, and Israeli or U.S. military action against Iran.

The forecast at present is not positive for proponents of détente. In the lower chamber of the U.S. Congress, the House of Representatives has already passed a sanctions bill, while in the upper chamber, the 100-member Senate reached 59 co-sponsors for its own sanctions bill, S. 1881.

President Obama vowed to veto the sanctions bill during his State of the Union address in January, taking heed to Iranian Foreign Minister Javid Zarif’s warning that this would kill the nuclear negotiations. The U.S. Constitution allows Congress to override a president’s veto with a two-thirds majority of votes in both chambers however. This is highly probable in the House and would require only 8 additional votes in the Senate in order to be achieved.

Domestic pressure groups are heavily weighted in favor of increased sanctions. The American Israel Public Affairs Committee (AIPAC), the most powerful domestic lobbying group on this issue, generated over $74 million in revenue in 2011 and boasts the attendance of half the U.S. Senate and one third of the U.S. House of Representatives at its annual policy conference. Its annual budget dwarfs its opponents’ combined operating budgets.

AIPAC did recently suffer a setback in its efforts to secure a Senate vote for additional sanctions. S. 1881, the bill sponsored by Senate Foreign Relations Committee Chairman Robert Menendez, Senator Mark Kirk, and Senator Chuck Schumer stalled at 59 signatures. Schumer and Menendez then backed away from their support of the bill but recently signed on to a letter that is likely to build momentum for new sanctions legislation if the negotiations do not bear fruit by July.

Their tactical withdrawal is reflective of the strong opposition from the Obama administration to new sanctions during the current diplomatic window; support for the administration from key Senate leaders including Senate Majority Leader Harry Reid, Senate Select Intelligence Committee Chairman Dianne Feinstein, and Senate Armed Services Committee Chairman Carl Levin (who is retiring this year); congressional recognition of the risks of terminating the negotiations; and outside support for the administration from high level Democratic Party donors, organizations including the Center for American Progress, and senior party leaders including likely 2016 U.S. presidential candidate Hillary Clinton.

Even if the Obama administration does secure a comprehensive nuclear agreement with Iran, the harshest sanctions against Iran were passed by Congress and require a congressional vote to undo. This could prove difficult if Congress views whatever deal the administration may negotiate as not going far enough in dismantling Iran’s domestic nuclear enrichment capability and maintaining a monitoring and inspections regime. If progress stalls due to a lack of compromise on either side, U.S.-Iran relations will again begin to deteriorate and make the risk of war more likely.

Ultimately the decision to use military force against Iran would rest with President Obama after receiving authorization from Congress. While he is unlikely to make this decision without the provocation of an Iranian dash for nuclear weapons, Congress could push the U.S. toward war by passing more constrictive sanctions in an attempt to present an existential threat to the Iranian government.

Such a move could prove self-defeating if the intended purpose of sanctions is to increase the United States’ diplomatic leverage with Iran. Analysts have warned that if the U.S. begins to be viewed in the eyes of the international community as the intransigent party in the negotiations, it could lead to the breakup of the international sanctions regime, which depends on continued enforcement by major importers of Iranian oil such as China and India. While these countries would not likely risk flouting the sanctions regime, which could result in their companies losing access to U.S. markets, they might respond by enforcing sanctions with greater laxity, helping to keep Iran’s economy afloat and current government in power.

Increased sanctions could also provoke defiant reciprocity from Iran. The Iranian parliament has threatened to pass a resolution calling for increasing uranium enrichment levels to 60 percent, reportedly the level needed to power nuclear submarines and closing in on the 90 percent level needed for nuclear weapons.

A major issue of contention in Congress is the fact that the Joint Plan of Action does not cover Iran’s alleged nuclear weapons delivery vehicle research, parts of which have dual civilian uses. State Department Under Secretary for Political Affairs Wendy Sherman attempted to reassure legislators during a Senate Foreign Affairs Committee hearing on February 4 that this issue will be addressed with the Iranian government in the course of the negotiations. Iran currently possesses medium-range missiles capable of reaching U.S. military facilities in the region as well as the military bases and cities of U.S. strategic partners including Saudi Arabia and Israel.

More problematic is the continued absolutist rhetoric of Ayatollah Ali Khamenei, the Supreme Leader of Iran, who by all accounts still maintains control of the Islamic Revolutionary Guard Corps (IRGC), an ideologically driven military forged in the fire of the 1980-1988 Iran-Iraq War. Senior Iranian national security officials who held leadership positions during the Iran-Iraq War are still incensed that the U.S. secretly backed Iraq against Iran, even turning a blind eye to Iraq’s use of chemical weapons against Iranian troops.

Khamenei himself is highly paranoid toward the U.S. and believes that while the Rouhani administration’s diplomatic team negotiates with its American counterparts, the U.S. is continuously seeking opportunities to overthrow the Islamic Republic and return Iran to its pre-revolutionary position in the American order in the Middle East.

Despite the Rouhani administration’s charm offensive toward the West and recent expression of willingness to accept a two-state solution between Israel and the Palestinians, the Islamic Republic of Iran under Khamenei’s orders continues to support Hezbollah in Lebanon, which it founded in the early 1980s and has spent decades funding to challenge the State of Israel’s political existence. Since Israel’s war with Hezbollah in 2006, Hezbollah has vastly expanded its rocket arsenal in preparation for another conflict.

In sum, structural forces on both sides militate against a negotiated solution. These forces do not preclude a positive diplomatic outcome but they will make it difficult to achieve and sustain one.

Businesses with investments in the U.S. should therefore understand the serious financial and reputational risks associated with investing in Iran at present. Those with investments or supply chains dependent on the health of the Iranian economy or access to strategic sectors of it should follow the domestic debates on both sides of this issue carefully.

The negotiations have a high probability of collapsing under pressure for increased sanctions from the hardliners in the U.S. Congress due to insufficient compromise from Iran; conversely, Iranian hardliners may pressure unrealistically for greater concessions from the U.S.. If this mutually reinforcing dynamic stalls the current diplomatic momentum, the probability of war will also increase, with the potential for targeting of oil facilities and shipping in the Gulf, as occurred during the 1980-1988 Iran-Iraq War.

By Thomas Buonomo, Research Analyst, Hart Energy Consulting