The parliamentary election will see a Western-backed coalition compete for support against an alliance led by Hezbollah, the Shia Muslim armed political group backed by Syria and Iran.
Rula Amin, Al Jazeera's correspondent in Beirut, said: "Clinton wants the pro-western coalition, March 14, to have enough seats to get a say in what happens in Lebanon.
"Critics have pointed out that Clinton expressing concern that Hezbollah and its allies might win is interference in itself."
She said: "Since 2006, the US has pledged over $1bn in aid to Lebanon, including $400m to the security forces.
"So, in a way, they [the US administration] are saying that this money is at stake - that Lebanon's relations with the US are at stake - if Hezbollah wins."
"However, we have to remember that this election is a close race. Even if Hezbollah and its allies do win, they will only win with a majority of a few seats," she said.
"In the past few years, Lebanon has proved that it cannot be dominated by one party. All sides have to co-operate."
The US secretary of state's visit to Lebanon comes exactly four years after Syria pulled thousands of its troops from Lebanon.
A senior US state department official said Clinton's visit was primarily aimed at convincing the Lebanese that Washington's attempt to engage Syria and Iran would not adversely affect them.
"Our discussions with the Syrians are not coming at the expense of the support for Lebanon's independence," the official said.
Damascus ended its 29-year military presence in Lebanon following public outrage over the assassination of Rafiq al-Hariri, a former Lebanese prime minister, in February 2005.
Clinton also on Sunday re-affirmed Washington's support for the Lebanese army as the sole holder of military power.
"Our ongoing support for the Lebanese Armed Forces remains a pillar of our bilateral co-operation," Clinton said in a statement before she landed in Beirut.