Under such circumstances, it is hard to say whether the Obama administration could stand its ground on the Iranian nuclear issue and succeed in leaving a legacy.

The civil strife in Yemen and Israel's opposition to the Lausanne deal could also weaken the Obama administration's resolve to end the Iranian nuclear deadlock. In fact, the strongest criticism against last week's deal has come from Israel, which has long deemed the prospect of a nuclear-armed Iran a threat to its survival. On Sunday, Israeli Prime Minister Benjamin Netanyahu denounced the agreement as a "bad deal". On the other hand, the deepening of the Yemen crisis could cast a shadow on the prospect of inking a final deal between Teheran and the six world powers.

On March 26, just hours before the Lausanne talks started, some Arab countries led by Saudi Arabia launched air strikes on Yemen targeting the strongholds of Houthis, who are believed to be supported by Iran. This military offensive could be seen as a public display of Arab countries' discontent with the possible easing of tensions between the US-led West and Iran.

Yet now that Washington and Teheran both have shown strong political will to negotiate a long-term deal, they should keep the current momentum going and strive to ensure that a final agreement is reached before the deadline, because with the Middle East already mired in crises, the world cannot afford to miss this opportunity to restore peace on least one front.

The author is a senior writer with China Daily.

wanghui@chinadaily.com.cn