"We have been engaged in an ongoing way and monitoring the global oil situation, particularly in light of the respective sanctions that we've had on Iran and its effect on oil markets. We'll continue that monitoring. I'm sure that the leaders will discuss the range of options that they might have before them," Donilon said.
"They'll also be pressing the Iranians to take advantage of the diplomatic efforts that we're putting forward," notably May 23 talks in Baghdad between Iran, on the one hand, and the United States, Britain, France, Russia, China and Germany (the so-called "P5+!") on the other.
The leaders will also discuss North Korea, Myanmar and efforts to end Syria's bloody crackdown on opposition to President Bashar al-Assad.
On Saturday, the summit shifts to the worrisome state of the global economy, amid tensions in Europe over whether to pursue austerity to bring down soaring national debts or couple it with stimulus efforts to boost job growth, and over how to respond to the crisis in Greece.
The spotlight then turns to Chicago for the NATO summit; there, the focus will chiefly be on Afghanistan, America's longest war. Obama will meet Sunday with Afghan President Hamid Karzai. (Pakistan President Asif Ali Zardari is expected to attend the summit, but he will not get a separate sit-down with Obama, Donilon said.)
NATO is expected to agree on a path for taking on a supporting role in the war-torn country next year while handing off the bulk of the fighting to Afghan forces. It is also expected to discuss who will cover the costs of the conflict after 2014, expected to run $4 billion per year, though an actual agreement is not expected until a conference in July in Tokyo. And it is expected to take up what sort of presence the alliance will have in Afghanistan after 2014.
"So Chicago is a critical milestone in the next step towards a responsible ending of this war," Donilon said.
NATO invited Zardari after Pakistani officials signaled that country was prepared to reopen supply lines to alliance forces in Afghanistan, which were shut down after a NATO air strike into Pakistani territory in November killed 24 Pakistani troops. Islamabad had said it wanted a formal apology from the United States and pushed for an end to drone strikes on its soil.
"We have made real progress, I think, towards resolving the issue around opening up the ground supply lines," Donilon said. "Whether that will be done in the next few days or not, I can't judge at this point. But there's been a decision, on both sides, to reach a conclusion of this."
And Donilon played down the absence of an Obama-Zardari meeting on the schedule. "There are 61 countries going to be present there, and the president is not going to have bilaterals with all them…but he will see him, obviously."
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