The United States Wednesday demanded the immediate release of two Israeli soldiers captured by Lebanese Hezbollah guerrillas, and said it holds Iran and Syria responsible for the new outburst of Middle East violence. Secretary of State Condoleezza Rice is telephoning leaders in the region to try to ease the crisis.

The Bush administration is trying to orchestrate pressure on Hezbollah to release the two Israeli soldiers, while also ascribing blame for the latest crisis to Iran and Syria, which have supported the radical Shiite militia in southern Lebanon.

Israel sent ground troops into the region for the first time in six years after Hezbollah guerrillas captured two Israeli soldiers and killed several others in an explosion of border attacks.

Hezbollah has maintained control of the area along the Israeli border despite a U.N. Security Council resolution two years ago demanding that it disarm and allow Lebanese government forces to take over.

Both the White House and State Department condemned what they termed unprovoked Hezbollah actions and called for the immediate and unconditional release of the two Israelis.

State Department Spokesman Sean McCormack, as did a White House colleague, cited the past history of support for Hezbollah by Syria and Iran, and said it is time that the Lebanese government of Prime Minister Fuad Siniora faced up to the challenge to the country's sovereignty posed by Hezbollah.

"We would urge the government of Lebanon to speak out about this challenge to their credibility, their sovereignty," said McCormack. "This is a challenge from Hezbollah to the Lebanese people and to the Lebanese government's sovereignty, so we would urge them to speak out about that. We would urge them also to do everything that they can to see that these two soldiers are released immediately and unharmed."

Secretary of State Rice, in Paris for a big-power meeting on Iran's nuclear program, discussed the issue with her foreign minister colleagues, and spoke by telephone with among others Lebanese Prime Minister Siniora, Israeli Prime Minister Ehud Olmert and U.N. Secretary-General Kofi Annan.

In addition, two senior administration envoys, Assistant Secretary of State David Welch and White House Middle East policy chief Elliott Abrams are in the region on a previously-arranged mission and discussed the Lebanese situation Wednesday with officials in Cairo and Amman.

At the United Nations, Israeli Ambasador Dan Gillerman submitted a formal complaint to Secretary-General Annan describing the kidnapping of the two Israelis as an act of war.

He told reporters Israel sees the Lebanese government as the responsible party, given its unmet obligation under Security Council resolution 1559 to take control of the border and prevent such attacks. But the Israeli envoy said Hezbollah's foreign sponsors are also to blame:

"One cannot disregard the blood-stained fingerprints and the twisted minds of Iran and Syria, who are the main perpetrators, harborers, financiers and initiators of terror in this world," said Gillerman. "And what we've seen today is another escalation in the activity of the axis of terror, of Iran, Syria, and the Hezbollah which is threatening not only the stability on the northern border, not only Israel, but the whole region and the world."

Gillerman said Israel will not negotiate with Hebollah leader Sheikh Hassan Nasrallah, who said in Beirut he would only free the two Israeli soldiers as part of a prisoner swap that could also involve the Israeli soldier held for three weeks by Palestinian militants in Gaza.

In Damascus, Syrian Vice President Farouk al-Sharaa denied his country had a role in either the Lebanon or Gaza abductions and blamed Israel for the attacks. Sharaa said Israel's occupation of Palestinian territories provokes the Lebanese and Palestinian people and that is why he said there are resistance groups among both populations.