Political tensions are again at the boiling point in Lebanon as Hezbollah attempts an overt power grab this week, seeking to wrest the reins of the largely pro-Western central government from the hands of Prime Minister Fouad Siniora.

If Hezbollah pulls it off, forget about the prospects of a democratic, Western-leaning Lebanese government. Instead, Iran and Syria will be calling the shots in Beirut.

The White House sounded the alarm last week, warning of "mounting evidence" that Syria, Iran and Hezbollah "are preparing plans to topple Lebanon's democratically-elected government."

Syria 's Washington embassy said the accusations were "ludicrous" and "unfounded," claiming Syria doesn't interfere in Lebanon's internal affairs. (Guess Syria's 30-year occupation of the country doesn't count . . . )

Since the fighting between Israel and Hezbollah ended on Aug. 14, political tensions have skyrocketed between Hezbollah and the Lebanese government, leading to negotiations about political power-sharing.

On the one side is the March 14th group - a pro-Western coalition of Sunni and Druze Muslims and some Christian groups. This group, led by Siniora, controls the government with the largest bloc in parliament. It takes its name from the date of the demonstrations after the assassination of Lebanese ex-Prime Minister Rafik Hariri - protests that led to the departure of Syrian forces from Lebanon that spring.

The March 14th group wants Hezbollah disarmed and dismantled as a state within a state. It also seeks to replace Lebanon's pro-Syrian President Emile Lahoud. (Back in 2004, Damascus extended Lahoud's term to 2007.)

On the other side of the struggle is Hassan Nasrallah's Hezbollah and its allies, including ex-Gen. Michel Aoun's (Christian) Free Patriotic Movement and the Amal party, pro-Syrian Shiites led by Nabih Berri, the parliament's speaker.

Hezbollah has been clamoring for a "national unity" government since the end of this summer's war to replace the current Cabinet, a move sure to increase the influence of pro-Syrian lackeys - and turbo-charge the clout of pro-Iran Shia Lebanese.

With some polls showing Hezbollah with 70 percent backing, Nasrallah promises million-man street protests if Hezbollah doesn't get its "unity" Cabinet by next Monday.

Hezbollah now holds just 14 seats in the 128-seat parliament and two posts in the 24- member Cabinet. It can count on the support of three more ministers, but eight votes are needed to veto key decisions.

If Hezbollah gets added seats, it also wants to amend the election law, calling for early elections for parliament in expectation of gaining a majority there.

The pro-Syrian/Iranian and pro-Western camps are scheduled to meet today to discuss the crisis. If Nasrallah doesn't get his way, expect more violence like the five grenade attacks of recent weeks, increasing fear and intimidation among his opponents.

But if Hezbollah does get what it wants, forget about ever seeing it disarm, as required under numerous U.N. resolutions. Instead, we'll see more trouble along the Lebanese-Israeli border as soon as peacekeepers disappear.

Syria will turn this summer's military "victory" over Israel into a political one, avenging its 2005 retreat from Lebanon, gaining leverage over Israel - and helping keep its man, Lahoud, in place.

Lahoud would likely try to prevent Lebanese cooperation with the international tribunal investigating Hariri's assassination. Syrian intelligence officers, including some close to the ruling Bashar Assad regime, have been fingered in the hit.

If Hezbollah brings down Lebanon's government or blackmails its way into a reshuffling of power, Iran will gain a larger-than-ever say in Lebanon's affairs. Indeed, we'll confront an emerging arc of Iranian influence across the Middle East. From Damascus to Beirut and into the Palestinian territories - Iran will be better able to spread fundamentalism, stifle democracy, nourish Hamas/Hezbollah, diminish U.S. influence, isolate Israel and squeeze Iraq.

Peter Brookes, a senior fellow at The Heritage Foundation, is the author of "A Devil's Triangle: Terrorism, WMD and Rogue States."