North and South Sudan are at war. The reasons for the conflict are complex, but the solution is not: To stop the killing, the international community must arm South Sudan. Unlike interventions in Afghanistan and Iraq, the United States need not fire any shots. Just as we have provided weapons to support Israel but never put our own troops at risk, we can help bring peace to this region. We need only make sure that, for the North, attacking the South is a little bit harder than shooting fish in a barrel.

South Sudan is less than a year old. Its war with the North is the result of an imbalance of military power that has encouraged military adventurism. Omar al-Bashir, president of the North and a possible coup target, believes he can secure his future by bombing the South into submission instead of negotiating. For this reason, he has undertaken extensive bombing in South Sudanese civilian areas since January, killing hundreds — an act of war.

Although the South has a large, well-motivated ground army, it has no air force or antiaircraft weapons to defend its people. Southern leaders believe Bashir and his generals plan to invade, occupy oil fields and install a puppet government that will give them control over oil revenue lost when the South became independent.

The only way to end the North’s bullying and foster peace talks is to give the South the right tools: American antiaircraft weapons. If the United States provides the materiel, the South can end the North’s bombing campaign. Most Northern air force pilots are mercenaries — if they start taking heavy losses, they will leave Sudan quickly.

The decision to arm the South shouldn’t be controversial. The United States has provided more than $30 million per year in military technical assistance with bipartisan support from Congress to the Southern Sudanese army since 2006. I know because, as U.S. envoy to Sudan under President George W. Bush, I helped put the program in place. Because the Republic of South Sudan is a sovereign state, the United States can provide military assistance without the approval of the U.N. Security Council or the African Union.

Given the remarkably broad coalition of U.S. grass-roots organizations on the left and the right behind South Sudan, providing antiaircraft weapons could have broad support. Franklin Graham, son of Christian evangelist Billy Graham and head of relief organization Samaritan's Purse, called for the bombing of the North; a wide variety of humanitarian groups asked the U.N. security council for “escalated action” last month. If the United States does not act, the war could turn into a bloodbath as more southern cities are bombed — providing further fodder for critics of President Obama’s foreign policy in the heat of his reelection campaign.

But the risks of not acting are greater than those of further intervention. China provides advanced weapons to North Sudan, endangering any future relationship with the South, which has warned Beijing about playing both sides. China might protest if the United States armed the South, but not too loudly — U.S. involvement would end the conflict, which threatens Chinese investments in the North. To ensure tacit Chinese (and Arab) support, the South would have to agree only not to invade the North again.

For South Sudan, this would be a great deal. Although many hoped that Southern independence would bring peace to the region, it has not. In fact, the dispute over control of Southern Sudanese oil fields is one of the principal causes of the current war. The North has demanded $36 a barrel to transport the oil to Port Sudan, while the going international rate is less than $1. Because the South refused to pay the $36 fee, Bashir’s government began commandeering oil tankers as they left Port Sudan last year and selling the oil themselves, constructing a new pipeline to divert the oil from the southern line.

All revenue to the Southern government stopped in November. This past February, the South began shutting down all oil pumping. The North walked out of negotiations with the South in February and refused to return.

Diplomatic pressure will not move Bashir and his generals, who do not take promises of improved relations with the West seriously. The United States has promised three times — in 2003, 2006 and 2010 — to normalize relations with Sudan if the North would let the South leave voluntarily. It did, and we did not respond quickly enough. Now we have no credibility. Meanwhile, Bashir ridicules Security Council resolutions. “We will implement what we want,” he said Thursday. “What we do not want, no one can impose upon us.”

In the past three years, the Obama administration has engaged Sudan by getting Bashir to agree to a free and fair referendum on Southern separation and, last July, allow the South to peacefully become independent. Now that war has come, talking will not end it. Only redressing the imbalance of military might will convince Bashir and his generals that fighting won’t solve the two countries’ profound political crisis. The Obama administration must arm the South Sudanese with antiaircraft weapons to create a stalemate and get the North back to the negotiating table.

Andrew S. Natsios, George W. Bush’s former envoy to Sudan, is a professor at Georgetown University and the author of “Sudan, South Sudan, and Darfur: What Everyone Needs to Know.”

Read more from Outlook:

Five myths about Obama’s foreign policy

Can Obama keep Sudan from exploding?

Clooney and Prendergast: We can prevent the next Darfur

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