BRUSSELS -- France, joining Britain, is urging its European Union partners to meet this month and end an arms embargo on Syria, to allow weapons to be sent to the opposition there.
"We want Europeans to lift the arms embargo," President François Hollande of France told reporters as he arrived in Brussels for a European Union summit meeting.
Echoing earlier comments by his foreign minister, Laurent Fabius, Mr. Hollande said: "We are ready to support the rebellion, so we are ready to go this far. We must take our responsibilities."
Mr. Hollande said that Britain and France were in agreement. "We cannot allow a people to be massacred by a regime that for now does not want a political transition," he said.
The European Union pact on the embargo and on sanctions against Syria must be renewed every three months. France is moving for the next review to be held this month, rather than in May. "We have to go very fast," Mr. Fabius said, urging that the union try to shift the balance of forces in Syria in favor of the opposition before many thousands more people die.
The rebels are clamoring for antiaircraft and antitank weapons. A European supply line could alter the dynamics of the two-year Syrian civil war, which is believed to have cost the lives of 70,000 people, without ending the Assad family's decades of rule.
French and British officials have said that only once the Syrian president, Bashar al-Assad, understands that he is losing the battle will he agree to negotiate a political resolution with the opposition. And there is a sense that the Syrian Army is beginning to erode, offering a greater opportunity for change.
In February, the embargo was renewed despite British concerns, with Germany and Sweden especially arguing against escalating the civil war. But Britain did win agreement to relax the embargo to allow nonlethal but quasi-military aid, like armored vehicles. The issue is likely to come up in Brussels at the two-day meeting of European Union leaders, but their focus will be on the economy.
Mr. Fabius warned that France and Britain might act unilaterally if their European partners disagreed. Asked on France Info radio whether the two would arm the opposition if there was no agreement, Mr. Fabius said only that France was "a sovereign state" and that the two countries would jointly act "to lift the embargo."
"We cannot accept that this current lack of balance, with on one side Iran and Russia delivering arms to Bashar, and on the other rebels who cannot defend themselves," Mr. Fabius said. "Lifting the embargo is one of the only ways that remain to change the situation politically."
On Tuesday, Prime Minister David Cameron of Britain said that his nation would continue to adhere to the embargo for now, but that it might reconsider if its partners did not agree to lift the embargo. "It is not impossible that we'll proceed the way we see fit," Mr. Cameron said.
Britain and France pushed for intervention in Libya, and France recently intervened in Mali without European Union agreement. But they seem to be lobbying their European Union colleagues rather than declaring independence of European Union consensus.
The French public has been shaken by the bloody, vicious and seemingly stalemated civil war in Syria, with which France has historic ties, and there are new concerns about the stability of Lebanon, as thousands of refugees continue to pour out of Syria.
At the same time, concerns are growing that the Lebanon-based militia Hezbollah, with Iran's backing, is increasing its efforts to bolster the Assad forces. In a speech to a security gathering on Thursday, Israel's chief of military intelligence asserted that Hezbollah was training a popular army in Syria that numbered 50,000 men, which Iran and Hezbollah could use to protect their Syrian interests if Mr. Assad fell.
"Iran and Hezbollah are both doing all in their power to assist Assad's regime," the intelligence chief, Maj. Gen. Aviv Kochavi, said at the annual Herzliya Conference in Israel. "They support Assad operationally on the ground, with strategic consultation, intelligence, weapons." He added that the plan was to double the size of the popular army. Such numbers are impossible to confirm.
In a statement on Thursday, the British Foreign Office said that the international effort for a political solution in Syria "has little chance of gathering momentum unless the regime feels compelled to come to the negotiating table," and added, "They need to feel that the balance on the ground has shifted against them."
Referring to the arms embargo, the statement said, "We are not prepared to rule out any options to bring an end to the suffering of millions of innocent Syrians."
British and French officials say they also sense that Washington's strict opposition to helping the Syrian rebels militarily may be shifting in President Obama's second term.
The new secretary of state, John Kerry, made his first overseas tour recently, with Syria as a prime topic, and his stops included Britain and France. After the visit, French officials said they found him sympathetic to their views. While Mr. Kerry repeated that the United States would not arm the rebels, the country has sent medical and humanitarian aid, and the C.I.A. has been covertly training rebel groups in Jordan since last year, according to American officials.
The United States has opposed sending ground-to-air and antitank missiles, even from other nations like Qatar and Saudi Arabia, out of concern that those weapons will fall into the hands of more radical Islamist fighters and could be used against other American allies, like Israel and Jordan.
On Thursday, Germany's foreign minister, Guido Westerwelle, said in a statement that his nation was ready to discuss the issue. "If important partners in the European Union now think the situation has changed, and they think this makes it necessary to change the decisions on sanctions, we are, of course, prepared to discuss this in the E.U. immediately," he said.
Russia, which has supplied helicopters and other military equipment to the Syrian government, warned that sending arms to the rebels would violate international law.
Isabel Kershner contributed reporting from Jerusalem.
This article originally appeared in The New York Times.