President Obama indicated on Monday that he's not confident a ceasefire agreement will be able to stop South Sudan's civil war in the coming weeks, and said other steps may be needed to give warring factions the right incentives.

"We don't have a lot of time to wait; the conditions on the ground are getting much, much worse," Obama said before sitting down with Nkosazana Dlamini-Zuma, head of the African Union, Ethiopian Prime Minister Hailemariam Desalegn, Kenyan President Uhuru Kenyatta, Sudanese Foreign Affairs Minister Ibrahim Ghandour and Ugandan President Yoweri Museveni in Addis Ababa, Ethiopia.

An East African regional organization has been brokering peace talks, and set an Aug. 17 deadline for parties in the civil war to accept its plan.

"If we don't see a breakthrough by August 17, then we're going to have to consider what other tools we have to apply greater pressure on the parties," Obama said during a news conference in Ethiopia with Desalegn.

The United Nations is considering an arms embargo if a peace isn't reached, and the U.S. is weighing "additional sanctions," according to senior administration officials who on Sunday spoke to reporters traveling with the president on the condition of anonymity.

Obama is stepping in now to see how the U.S. can help, and to serve as a "mechanism for additional leverage on the parties, who, up until this point, have proven very stubborn and have not yet risen to the point where they are looking out for the interests of their nation as opposed to their particular self-interests," Obama said.

"Up until this point, it's been very useful to have the African countries take the lead," he explained. "As [Desalegn] stated, the more that Africans are solving African problems, the better off we're going to be."

Obama's advisors have been very frank about how disappointed they are that South Sudan went from triumphantly declaring independence four years ago to devolving into civil and ethnic war.

"I think the tragedy that we've seen is that there was this very long struggle for independence that ultimately drew our support," Ben Rhodes, deputy national security advisor for strategic communication, said on Sunday. "But once independence was claimed, the ability to transition from being a movement that sought independence to governing the country of South Sudan, that transition did not work.

"You can't fix everything in a country that has been so torn by conflict for so many decades, but I think we have an obligation to try to bring the parties to a better place and to give the people of South Sudan an opportunity for peace," Rhodes said.

"I don't think that anybody should have high expectations that this is going to yield a breakthrough," said another senior administration official in discussing Monday's peace meeting. "The parties have shown themselves to be utterly indifferent to their country and their people — and that is a hard thing to rectify."

At least one African leader who participated in the South Sudan meeting floated the idea of a “regional intervention force” if peace cannot be secured by Aug. 17, an administration official told reporters traveling with Obama during his five-day trip to Africa after the meeting.

The idea was not Obama’s and is not a set Plan B if the East African regional organization spearheading negotiations fails to convince South Sudan’s warring parties to lay down their arms, the official said.