American and Israeli diplomats warned the UN Security Council on Wednesday that the persistence of rocket attacks from Gaza into southern Israel presented an immediate threat to the fragile cease-fire in the region. Speaking at a regular meeting on the situation in the Middle East, Israeli Ambassador Gabriela Shalev insisted that the new government would not brook "a return to the status quo ante" of the six-month cease-fire period that preceded the start in December of the IDF's Operation Cast Lead against Hamas. "Tangible measures must immediately be taken against smuggling, as only concrete action will help to stabilize the region," Shalev demanded. American deputy permanent representative Alejandro Wolff said Hamas's behavior - both in terms of rocket attacks and arms smuggling through tunnels - was "threatening to set off another deadly round of violence." Wolff repeated US calls on on Israel to dismantle settlement outposts created since March 2001. The two spoke following a briefing by Lynn Pascoe, the undersecretary general for political affairs, who described the uneasy peace as "a worrying situation of impasse and uncertainty." "We call for an end to all acts of violence and for respect of international humanitarian law by all parties," Pascoe told the Security Council, speaking on behalf of the UN agencies. Pascoe raised concerns about the lack of concrete progress on key elements of the Security Council's own cease-fire resolution, passed in January, which called for the establishment of a durable cease-fire agreement, the opening of border crossings, access for humanitarian relief, the suspension of arms smuggling and progress toward reconciliation between Fatah and Hamas. He also reiterated the UN's demands that Israel increase the flow of humanitarian relief through border crossings into Gaza, a call repeated Wednesday in Jerusalem by Richard Serry, the UN's special coordinator for the Middle East peace process. Both Serry and Pascoe also called for restarting negotiations about the release of Gilad Schalit in exchange for Palestinian prisoners.