Mr. Tillerson flew straight from the summit in Italy to Moscow, carrying the G-7’s strong desire for a new start in Syria.

The Group of Seven industrialized nations on Tuesday urged Russia to pressure the Syrian government to end the six-year civil war, but rejected a British call to impose new sanctions on Moscow over its support of President Bashar Assad.

Foreign Ministers from the seven countries said Moscow can play a constructive role in ending the brutal conflict that has destabilized the Middle East, driven millions to escape Syria and further frayed relations between the West and Russia.

“Russia can be a part of that future and play an important role,” U.S. Secretary of State Rex Tillerson said.

Or, he added, it could maintain its alliance with Syria, Iran and militant group Hezbollah, “which we believe is not going to serve Russia’s interests’ longer term.”

Mr. Tillerson flew straight from the summit in Italy to Moscow, carrying the G-7’s strong desire for a new start in Syria, but few concrete proposals to make it happen.

The G-7 blames Assad’s military for a deadly chemical attack last week. Ministers meeting in the walled Tuscan city of Lucca strongly supported U.S. missile strikes that targeted a Syrian air base believed to have been used to launch the attack. But they were divided about how to deal with Syria, and Moscow.

Italian Foreign Minister Angelino Alfano, who hosted the G-7 gathering, said “there is no consensus for further new sanctions.”

“We must have a dialogue with Russia,” he said. “We must not push Russia into a corner.”

Instead of sanctions, the meeting’s final communique called for an investigation by the Organization for the Prohibition of Chemical Weapons to determine who was responsible for the “war crime.” The U.S. and Britain say there is little doubt Assad’s forces are culpable.

The group’s stance was a rebuff to British Foreign Secretary Boris Johnson, who said on Monday the G-7 was considering new sanctions on Russian military figures to press Moscow to end military support for the “toxic” Assad government. U.S. officials in Washington have also raised that prospect.

Others argued for a more conciliatory approach. German Foreign Minister Sigmar Gabriel said Russia, and Assad ally Iran, must be involved in any peace process to end Syria’s six-year civil war.

Mr. Gabriel said the United States had “sent a clear signal to the Assad regime” by launching cruise missiles at a Syrian air base, but said other nations should “reach out to Russia” rather than seek a military escalation.

“Not everyone may like it, but without Moscow and without Tehran there will be no solution for Syria,” he said.

The other G-7 members Germany, France, Britain, Canada, Japan and current president Italy are also trying to grasp what the U.S. administration’s foreign policy is, amid conflicting signals from Washington.

Mr. Tillerson’s trip comes after an American official said the U.S. has drawn a preliminary conclusion that Russia knew in advance of the chemical attack an allegation that heightens already acute tensions between Washington and Moscow.

Until Mr. Trump ordered U.S. missile strikes in response to the nerve gas attack that killed more than 80, the President had focused on defeating the Islamic State group and had shown no appetite for challenging Mr. Assad and, by extension, his Russian supporter President Vladimir Putin.

Even since the missile strikes, signals have been mixed.

After the April 4 chemical attack, Mr. Trump said his attitude toward Mr. Assad “has changed very much” and Mr. Tillerson said “steps are underway” to organize a coalition to remove him from power. But Mr. Tillerson also said that the top U.S. priority in the region remains the defeat of Islamic State militants.

On Monday Mr. Tillerson raised fresh expectations for aggressive U.S. action and not only in Syria as he visited the site of a World War II Nazi massacre in central Italy, saying the U.S. would hold to account “all who commit crimes against the innocents anywhere in the world.”

Though such comments hint at a more activist U.S. foreign policy focused on preventing humanitarian atrocities, Mr. Trump has consistently suggested he prefers the opposite approach. His new administration has generally downplayed human rights concerns while promoting an “America First” strategy de-emphasizing the concerns of foreign nations.

Uncertainty about objectives persisted as Mr. Tillerson met Tuesday on the sidelines of the Lucca meeting with diplomats from “like-minded” countries on Syria, including Turkey, Jordan, Saudi Arabia and the United Arab Emirates as well as G-7 members.

The U.S. hopes the regional countries can help ensure security and stability in Syria after the Islamic State group is defeated.

The G-7 members broadly agree that Assad should go but not necessarily when, or how. European leaders are especially conscious of the disaster in Libya, where an internationally backed ouster of dictator Muammar Gadhafi was followed by a descent into chaos and factional fighting.

Mr. Tillerson said on Tuesday that “It is clear to all of us that the reign of the Assad family is coming to an end.”

“But the question of how that ends and the transition itself could be very important in our view to the durability, the stability inside of a unified Syria.

“That’s why we are not presupposing how that occurs,” Mr. Tillerson added.