The US State Department said Friday that Americans in Lebanon should consider leaving when it is safe to do so, and officials made contingency plans for the evacuation of people who cannot leave on their own. "Our best advice is for people to assess their security situation," State Department spokesman Sean McCormack said. "Right now ... from the US government perspective, there aren't any reliable ways to get out by air, land or sea." Nonessential US Embassy personnel and family members have permission to leave because of rising violence between Israel and the Lebanese militia Hizbullah. The fighting has closed the Beirut airport and the city's seaport and has made road travel dangerous. No government employees have left, he said. The United States estimates 25,000 Americans live or work in Lebanon, but officials assume that far fewer would choose to leave if they could. "We would, as part of that planning, see how we can accommodate those American citizens who want to leave," McCormack said. Meanwhile, the Homeland Security Department urged state and local law enforcement officials in the United States to be watchful for attacks spurred by the violence in the Middle East. Homeland Security Secretary Michael Chertoff said there is no specific or credible intelligence to indicate any immediate domestic threats. Homeland Security and the FBI sent a joint bulletin to state security and law enforcement officials about people who "may be planning to act out on grievances or sympathies in the homeland," spokeswoman Michelle Petrovich said. "We urge vigilance during this heightened state of tension in the Middle East," Petrovich said. The State Department sent a message late Friday to American citizens who had registered with the US Embassy as traveling to or already in Lebanon. The United States is "working on options to facilitate the departure of private Americans who wish to depart and would require assistance in doing so, but these plans are not yet finalized," the message said. In Washington, the Arab American Institute, a community and policy advocacy group for Arab-Americans, said it was receiving telephone calls and e-mails from Americans trapped in Lebanon and Gaza and urged the State Department to mount an evacuation from both places. The institute said the fighting is occurring in a season when many Arab-Americans travel to the Middle East to visit their relatives. The Defense Department said it had received no request for help with an evacuation. Pentagon officials said they expect a request soon, and they were watching developments closely and studying options for how to remove the Americans.