United States and world officials are naturally wary about the future of relations be-tween Lebanon and Syria after this week’s assassination of the former Lebanese prime minister. Given the interconnectedness and complexity of Middle Eastern affairs, any sanctions or retaliatory action must be well thought out.

While there is yet to be proof that Syria was involved in Monday’s killing of Rafik Hariri, a billionaire businessman and moderate politician, fingers are already pointing in that country’s direction. With good reason. Mr. Hariri was once an ally of Syria but had severed ties with the neighboring country when he resigned the Lebanese prime minister post in October to protest Syria’s push to alter the Lebanese

constitution to allow the current president, Emil Lahoud, to serve another three years.

Mr. Hariri, who was killed in a massive car bombing in Beirut that also took the lives of 13 other people and injured more than 100, further angered Syria by advocating for the passage of a United Nations Security Council resolution demanding the withdrawal of Syrian troops from Lebanon. The forces, now numbering 15,000, arrived in Lebanon in 1976 to quell a civil war. The fighting lasted for nearly 15 more years before a peace agreement was reached in 1990.

Despite the end of the war, Syrian forces remain in Lebanon, prompting many to complain that Damascus is stifling Lebanese democracy. Elections are scheduled for May and Mr. Hariri was being coaxed to lead a campaign based on the ouster of Syrian troops.

There are further problems with Syria, including the belief among U.S. and other leaders, that it is supporting insurgent fighters in Iraq and Palestinian militants who are attacking Israelis. Secretary of State Condoleezza Rice acknowledged that the U.S. decision Tuesday to recall its ambassador to Damascus was based on more than the killing of Mr. Hariri.

Further complicating the matter are the rejuvenated Israeli-Palestinian peace process. The negotiations could permanently leave a half million Palestinian refugees in Lebanon, a major concern due to the poverty and anger of the refugees. Syria has reason to destabilize the peace process because its presence in Lebanon gives it a major bargaining chip with the Israelis who believe extremist groups launch attacks from Lebanon. These issues must be addressed as part of the peace process, largely guided by the United States.

Another problem is Syria’s economic problems. While the Syrian economy is struggling, Lebanon’s has been rebuilt after the years of civil war. The gleaming buildings along Beirut’s waterfront were a symbol of Mr. Hariri’s success, as both a politician and construction magnate. This gives Syria more reason to try to maintain control over its neighbor’s policies.

An investigation into Mr. Harrir’s murder, which Syrian, Lebanese and U.N. officials have called for, should be begun immediately. If it is found that Syria had a role in the killing, sanctions and further diplomatic pressure are in order. The same steps are likely to be necessary, in the absence of a Syrian link, to force the country to give up its current role of Middle East destabilizer.