The timing of the resolutions, which officials described on Tuesday on condition of anonymity because negotiations are not final, is intended to highlight recent allegations that Syria is funnelling weapons and stirring up trouble in Palestinian camps in Lebanon.
US Secretary of State Condoleezza Rice discussed Syria and Lebanon during an unannounced breakfast with UN Secretary-General Kofi Annan on Tuesday.
"It was a good opportunity for her to raise the issues surrounding the calendar," US State Department spokesman Sean McCormack said afterwards.
Anti-Syrian politicians in Lebanon blame Syria for the assassination of former Lebanese prime minister Rafiq al-Hariri, a charge Syria denies. UN investigator Detlev Mehlis is to release a report on the inquiry into the killing by 24 October.
Mehlis has named four pro-Syrian Lebanese generals as suspects and questioned seven Syrian officials, one of whom - Interior Minister Ghazi Kanaan - reportedly committed suicide last week.
Two measures are in the works, one of which recommends what to do with Mehlis' report. The other concerns US allegations that Syria is supporting anti-Israeli fighters in Palestinian refugee camps inside Lebanon.
Both UN measures would probably be sponsored by France, a former colonial power in Lebanon. The reports are expected to be taken up by the Security Council next week.
Syrian President Bashar al-Assad
denies any part in al-Hariri's death
Also in the works is a report on Syrian compliance with joint US-French-sponsored Security Council resolution 1599 last year that demanded the withdrawal of Syrian troops from Lebanon.
The US State Department's McCormack said US officials wanted to discuss both reports with other council members and other countries.
The goal, he said, was to review "what actions, what further steps, if any, might be warranted by what's contained in the reports. But we have to see what's in the reports first".
Rice shuttled among Paris, Moscow and London last week for discussions that included the Syria-Lebanon question six months after Syria withdrew forces from its much-smaller neighbour.
Syria was the dominant military and political force in Lebanon for nearly three decades, and the Bush administration charges that Syrian intelligence agents remained there.
The US is also at loggerheads with Damascus over its alleged support for Iraqi fighters, accusing it of failing to do enough to stop foreign fighters from crossing into Iraq.
Lebanese urge tribunal
Separately on Tuesday, a Lebanese judge charged a former Syrian intelligence officer accused of lying to UN investigators in the al-Hariri case.
Al-Hariri supporters also began lobbying foreign embassies representing United Nations Security Council members to back their call to set up an international tribunal to try those responsible for his murder.
Interior Minister Ghazi Kenaan is
said to have committed suicide
One of the new UN measures would seek an extension of Mehlis' mandate, a US official said, perhaps to continue investigation or to refer his findings to some kind of court or tribunal.
The Lebanese government has asked to extend the Mehlis investigation, but a UN diplomat, speaking on condition of anonymity, said Lebanese officials were divided about whether to expand it to cover the apparent suicide of Syria's interior minister and the assassination and attempted assassination of journalists.