President Barack Obama and Secretary of State Hillary Clinton late Sunday urged the new Lebanese government to cooperate with a United Nations tribunal investigating the assassination of Lebanese premier Rafik al-Hariri.

For the past two years, a bitter political battle has revolved around the Special Tribunal for Lebanon (STL), a controversial U.N.-backed court expected to implicate members of the Iranian-backed Hezbollah in the Hariri murder.

Hariri and 22 other victims killed in a car bombing Feb. 14, 2005.

“Ending the era of impunity for political assassinations is essential to realizing the justice and stability that the Lebanese people deserve, and any attempt to interfere with the Tribunal’s work or fuel tensions within Lebanon must not be tolerated,” Obama said in a statement issued on the eve of the sixth anniversary of Hariri’s killing, according to AP.

“The cause for which prime minister Hariri and so many Lebanese patriots gave their lives must remain our guide,” he said.

“Any attempt to interfere with the tribunal’s work or fuel tensions within Lebanon must not be tolerated,” Obama said

Hezbollah, the Shiite armed group, and its allies walked out of the previous government after then-Prime Minister Saad al-Hariri – the slain man’s son – refused to denounce the tribunal.

“At this critical moment, we call on all friends of Lebanon to stand with the people of Lebanon, who must be free to determine their own destiny,” Obama said.

Hezbollah may be in a position to block the court’s work after its favored candidate, Najib Mikati, was named Lebanon’s new prime minister.

“This is a decisive moment for Lebanon,” Clinton said in separate statement on Sunday. “Those who would try to block Lebanon’s cooperation should desist and show a measure of human decency. Ultimately, without justice, there can be no peace and stability for Lebanon.”