US Secretary of State Condoleezza Rice has paid an unexpected visit to Beirut to support "the new Lebanon that should be free of foreign influence".
President Lahoud is known as pro-Syrian
She met pro-Syrian President Emile Lahoud after paying her respects at the tomb of former Prime Minister Rafik Hariri and meeting his son.
Ms Rice's visit came days after a new Lebanese government was formed.
The cabinet emerged from the first elections in 30 years to be held without Syrian troops in Lebanon.
Damascus completed its withdrawal following Lebanese and US pressure in the wake of Mr Hariri's assassination.
Many Lebanese blamed Syria for the car-bomb attack on the former prime minister in February - an allegation denied by Damascus.
'History of blood'
Ms Rice is on hastily-arranged three-day visit to the Middle East.
"What I am here to do is to support the new Lebanon. And the new Lebanon is one that is democratic," she told a news conference after talks with Prime Minister Fouad Siniora.
"It is a Lebanon in which Lebanese should make decisions for the Lebanese, it is one that must have international obligations that we fully expect to be carried out."
The secretary of state said the US would not change its policy on the Shia militant movement Hezbollah which has a minister in the Lebanese government.
"The United States has a long-standing policy towards Hezbollah that has a history to it, that has a history of blood to it and that has not changed," she said, urging the prime minister to disarm its militants in line with a Security Council resolution.
Mr Siniora said the Lebanese would hold "strong as well as serious discussion and dialogue" on disarming Hezbollah, but called for "understanding and patience".
Earlier, Ms Rice said the US "would like to see the day when there are good neighbourly relations between Syria and Lebanon based on mutual respect and equality".
Rice paid tribute at the tomb of ex-Prime Minister Rafik Hariri
"But good neighbours don't close their borders to their neighbours," she said in a reference to recent measures by Syria to tighten cargo traffic from Lebanon.
"It is a very serious situation on the Lebanese border where Lebanese trade is being strangled," said the US secretary of state.
She met Israeli Prime Minister Ariel Sharon on Friday morning and is expected to have talks with Palestinian leader Mahmoud Abbas on Saturday.
The visit to the region follows a surge in Palestinian-Israeli violence and mass protests by Israelis opposed to the withdrawal, set for mid-August.
Ms Rice appears to have cleared her schedule for Friday after the meeting with Mr Sharon to make time for the visit to Lebanon.