The United States is poised to significantly expand its non-lethal military aid to the Syrian opposition as European nations weigh easing an arms embargo to potentially supply the rebels with arms and increase pressure on President Bashar Assad to step down.

   The European Union arms embargo expires at the end of May and may be allowed to expire or be modified to only block weapons that are headed to Assad's government.

   If that happens, it will amount to a new threat to give weapons to the rebels, and test whether the Syrian president reacts to the increased pressure _ or if stronger international intervention might be tried.

   U.S. Secretary of State John Kerry is expected on Saturday to announce plans to give opposition forces up to $130 million in defensive military supplies _ possibly including body armor, armored vehicles, night vision goggles and advanced communications equipment. U.S. officials said exactly what is given, and how much it will cost, will be determined at a Saturday meeting Kerry will attend in Istanbul, Turkey, of the Syrian opposition leadership and their main international allies. He left Washington for Turkey late Friday.

   The administration will work with opposition leaders to determine their needs before decisions are made, the State Department said. Among the options being discussed: assistance for the expansion of ongoing, civilian-led programs to support delivery of critical goods and services by local councils throughout Syria and more aid for capacity-building efforts.

   The additional non-lethal assistance would be provided to such moderate opposition groups as the Syrian Opposition Coalition, local councils, civil society organizations and the Supreme Military Council, the State Department said.

   The U.S. officials spoke on condition of anonymity because they were not authorized to preview Kerry's announcement publicly.

   On Thursday, Kerry said the conference aims to get the opposition and all prospective donors ``on the same page'' with how Syria will be governed if and when President Bashar Assad leaves power or is toppled.

   ``The hope is that that will then create a confidence level about who is getting what kind of aid from whom,'' he told the Senate Foreign Relations Committee.

   With Syria's civil war in its third year, the U.S. and its European and Arab allies are struggling to find ways to stem the violence that, according to the United Nations, has killed more than 70,000 people. Despite international pressure, Assad has managed to retain power far longer than the Obama administration first expected.

   ``We need to change President Assad's calculation, that is clear,'' Kerry said. He said the government's survival largely depends on the continued support it gets from Iran, its proxy Hezbollah, and Russia.

   ``That equation somehow has to change,'' Kerry said.

   He said boosting the size and scope of non-lethal assistance to the rebels is one way to convince Assad that he must go.

   Despite pressure from Congress and even advisers within his own administration, President Barack Obama has said he has no plans to send weapons or give lethal aid to the rebels.

   Instead, the U.S. has been shipping food and medical supplies directly to the Free Syrian Army since February and later expanded the aid to include defensive military equipment. So far, the U.S. has provided an estimated $117 million in non-lethal aid to the Syrian opposition, said White House National Security Council spokeswoman Caitlin Hayden.

   Sen. John McCain, one of the top Republicans on the Senate Armed Services Committee, renewed his call Thursday for U.S. military action in Syria, including airstrikes on government aircraft and weapons but not sending in American soldiers. He said the steps he recommends would give moderate and secular opposition forces a better chance to succeed without having to depend on extremist groups that are supporting the rebels.

   ``Do the costs of inaction outweigh the costs of action? I believe they do,'' McCain said at the Center for a New American Security in Washington. ``And as much as I hate war and wish to avoid it, I believe this conflict will grind on with all of its worsening effects until the balance of power shifts more decisively against Assad.''

   The U.S. is not opposed to other countries arming the rebels _ provided there are assurances the weapons do not get to extremist groups that have gained ground in the conflict.

   In Europe, Britain and France are leading a push to modify the European Union's arms embargo on Syria to permit weapons transfers to the rebels by the end of next month. The EU embargo is to expire at the end of May unless it is extended or revised.

   Those in favor of the change say there have been no decisions on whether to actually supply the rebels with arms. They argue that allowing such transfers would increase the pressure on Assad. U.S. officials say they support testing this strategy.

   Germany and the Netherlands, however, are said to be reluctant to support the step because they fear it would lead to further bloodshed.

   Amal Mudallali, a Syria scholar at the Woodrow Wilson Center in Washington, said it's unlikely Assad will leave any time soon. She noted that Syrian forces have stepped up counterattacks against the rebels in recent days, and she predicted the fighting would have to dramatically shift against Assad for him to go.

   ``If the EU lifts the embargo, maybe this will change things on the ground, but I am not sure it will change the American position,'' Mudallali said. ``But it will put pressure on the Americans because they don't want to feel they are behind on things. It will show people in the region that the Americans are not leading on this _ that the EU is.''

   In an interview Thursday, the EU's top official for humanitarian aid said arming the rebels or otherwise giving them deadly aid could create a backlash by the Assad government and, in effect, worsen the situation for the Syrian people.

   EU Commissioner Kristalina Georgieva said she does not advocate a position on whether the international community should arm the rebels or not. She maintained efforts to promote diplomacy through dialogue have not yet been fully exhausted.

   ``Because the Syrian government, the Assad government, has very strong military and chemical weapons, we have to be fair and say there is a risk in Syria that an external use of force may trigger to the detriment of the Syrian people,'' Georgieva said. ``It may get worse.''

   Kerry said that Assad, his inner circle and supporters in Iran and Russia have yet to be persuaded to enter negotiations with the opposition and allow for a political transition. He said he had not given up on persuading Moscow to reverse its support for Assad, and would be meeting with Russian Foreign Minister Sergey Lavrov next week in Brussels on the sidelines of a NATO-Russia Council meeting.

   ``My hope is still that the Russians can be constructive,'' he said. (AP)