Diplomats attempting to negotiate an end to Syria's bloody civil war said Thursday that they had agreed to try and implement a temporary "cessation of hostilities" in a week's time as Russia's prime minister warned that the use of foreign ground troops in the conflict could result in world war.

U.S. Secretary of State John Kerry hailed the agreement as a significant accomplishment. However, the ISIS and al Nusra Front terror groups will not be involved in the truce - and Russia has said it will be continuing its bombing campaign.

Kerry himself admitted that the agreements were "commitments on paper" only, adding that a cessation-of-hostilities agreement would only be a "pause" in fighting and that more work would need to be done to turn it into a full-fledged cease-fire.

"The real test is whether or not all the parties honor those commitments and implement them," he told reporters after the nearly six-hour meeting at a Munich hotel, which ran into the early hours of Friday.

Although foreign ministers from the International Syria Support Group managed to seal an agreement to "accelerate and expand" deliveries of humanitarian aid to besieged Syrian communities beginning this week, their failure to agree on a hard-and-fast cease-fire leaves the most critical step to resuming peace talks unresolved.

Kerry his Russian counterpart, Foreign Minister Sergey Lavrov, said the U.S. and Russia would co-chair both a working group on humanitarian aid as well as a task force that will try to deal with the "modalities" of the temporary truce. That task force will include members of the military along with representatives from countries that are supporting various armed groups in Syria. The Syrian government and the opposition would both have to agree to the details.

The deal appeared to be the result of a compromise between the United States, which had wanted an immediate cease-fire, and Russia, which had proposed one to start on March 1. The U.S. and others saw the Russian proposal as a ploy to give Moscow and the Syrian army three more weeks to try to crush Western- and Arab-backed rebels. The U.S. countered with demands for an immediate stop to the fighting.

Late Thursday, Russian Prime Minister Dmitry Medvedev was quoted as saying in an interview published by the German newspaper Handelsblatt that "a ground operation draws everyone taking part in it into a war."

When asked about a recent proposal from Saudi Arabia to send in ground troops to Syria, the prime minister answered that "the Americans and our Arab partners must consider whether or not they want a permanent war."

Despite apparent concessions on potential timing of the truce and the agreement to set up the task force, the U.S., Russia and others remain far apart on which groups should be eligible for it. The new task force will take up a job that was supposed to have been settled months ago.

Russia, Syria and Iran argue that other groups, notably some supported by Turkey, Saudi Arabia and other Arab states, should not be eligible for the cease-fire, and there was no sign Friday that those differences had been resolved.

Lavrov also said the Russian air campaign in support of Assad's military would continue against terrorist groups and denied persistent reports that the Russian strikes have hit civilian areas, notably around rebel-held Aleppo, where heavy fighting has been raging for the past week.

Among the issues the task force is charged with sorting out are delineating territories held by ISIS, al-Nusra and other militant groups, ensuring the compliance of eligible parties and referring violations of the truce for appropriate action, including exclusion from the arrangement.

Asked Friday to comment on the Munich talks, Salem Meslet, the spokesman for the Syrian opposition coalition known as the High Negotiations Commitee, said, "We must see action on the ground in Syria."

Five years of conflict have killed more than a quarter-million people, created Europe's biggest refugee crisis since World War II and allowed the ISIS to carve out its own territory across parts of Syria and neighboring Iraq.

Overall, the United Nations says almost half a million people are besieged in Syria. Since the beginning of 2015, Syria's government had approved just 13 inter-agency aid convoys, out of 113 requested, the U.N. reported last month.

As Kerry met with the Syria group in Munich, U.S. Defense Secretary Ash Carter was in Brussels to rally fresh support for the fight against the Islamic State group in largely the same territory.

Carter said defense ministers from more than two dozen countries gave a "broad endorsement" of a refined U.S. plan for defeating the Islamic State. After a meeting at NATO headquarters, Carter told reporters that nearly all participants either promised new military commitments or said their governments would consider new contributions. He predicted "tangible gains" in Iraq and Syria by March.

"We will all look back after victory and remember who participated in the fight," he said, appealing to coalition partners to expand and deepen their military contributions.

NATO Secretary-General Jens Stoltenberg said the alliance agreed Thursday to deploy NATO airborne command and control aircraft in order to free up similar U.S. aircraft for the air campaign in Syria and Iraq.

The Associated Press contributed to this report.