Updated

The Iranian-backed militant group Hezbollah denied Thursday that it placed any demands on the billionaire businessman it chose to become prime minister of Lebanon.

Hezbollah and its allies toppled Lebanon's Western-backed government two weeks ago and secured enough support in parliament to name Najib Mikati as their pick for prime minister. Critics have expressed concern that Mikati will be beholden to the militant group's demands — something Mikati has also denied.

"We did not give a list of conditions to Prime Minister Mikati," the head of Hezbollah's 12-member bloc in parliament said. "What we asked for is a national partnership and a national salvation government in which everyone cooperates for the interest of the country."

Mikati has emphasized that he wants a unity government and will not do the bidding of any one side in Lebanon's fractious politics. Opponents of Hezbollah — which the U.S. considers a terrorist organization — say having an Iranian proxy at the helm of Lebanon's government would lead to international isolation.

On Thursday, Mikati met with U.S. Ambassador Maura Connelly just days after Washington warned that the formation of a government dominated by Hezbollah would mean changes in relations with Lebanon.

The 55-year-old telecom tycoon "confirmed during the meeting the importance of bilateral relations between Beirut and Washington," he said in a statement as he began the process of forming a new government.

Also Thursday, Mikati's opponents pushed him to state his position on an issue that is at the heart of Lebanon's political crisis: a U.N.-backed tribunal expected to accuse members of Hezbollah of involvement in the 2005 assassination of former Prime Minister Rafik Hariri.

Hezbollah denies any links to the killing and calls the court a conspiracy by the U.S. and Israel. The group and its allies walked out of the previous government when then-Prime Minister Saad Hariri — the slain man's son — refused to denounce the tribunal and cut off Lebanon's 49 percent share of the funding for it.

Saad Hariri has called the walkout a "coup d'etat" and insisted he will never join a government led by a candidate chosen by Hezbollah — suggesting the country could be in for a prolonged stalemate.

Hariri ally and former premier Fuad Saniora on Thursday called on Mikati to put into writing exactly what his stance is on the tribunal. Mikati did not immediately respond, but in recent days he has said he would make a decision based on dialogue with all sides.

Saniora also spoke about Hezbollah's weapons, a contentious issue in Lebanon. Hezbollah insists that it needs to maintain its arsenal to ward off any threat from Israel. But the weapons make Hezbollah the most powerful military force in the country — far stronger than even the national army.

Saniora said the weapons should be put under the control of Lebanese authorities.

"There should be a commitment that the use of any weapons in Lebanon should be restricted of Lebanese authorities," he said in a press conference.

In neighboring Syria — Hezbollah's other foreign patron, besides Iran — Foreign Minister Walid al-Muallem urged all sides to join a unity government.

He spoke at a press conference with Britain's Foreign Secretary William Hague, who arrived in Syria late Wednesday to hold talks about political developments in Lebanon and the stalled Middle East peace process.

Hague said he discussed the threat posed by Iran's nuclear program and risks of broader proliferation in the Middle East.