With Europe pushing to arm the anti-government rebels in Syria and President Obama reportedly seeking plans for a no-fly zone over the war-torn country, the United States is inching closer to intervening directly in a conflict in which more than 70,000 people have already died.

White House officials insist that Obama has made no decision on providing arms to the Syrian rebels or establishing a no-fly zone there, saying all options remain on the table. But recent developments are ratcheting up the pressure on the president to use American force to help end the two-year-civil war.

The European Union voted to lift its arms embargo on the Syrian opposition, hoping the sign of unity would bring Syrian President Bashar al-Assad's regime to the negotiating table. At the same time, however, Russia vowed to provide Assad's regime with advanced missiles, stoking fears of more violence in an already hostile region. And Israel said it would strike down such air defense missile systems if they were delivered to Syria.

As American allies move toward deeper intervention, the White House instructed the Pentagon to devise plans for a no-fly zone in Syria, the Daily Beast reported on Tuesday, citing two administration officials. The White House would not comment on the report.

The White House did acknowledge Tuesday that it knew Sen. John McCain, R-Ariz., was making a secret Memorial Day trip to meet with the Syrian rebels but declined to say whether Obama's one-time political rival -- and a vocal critic of the White House's handling of Syria -- was carrying a message from the president. McCain, the first senator to travel to Syria since the civil war began, wants Obama to provide lethal weaponry to the anti-government rebels there -- and the Senate Foreign Relations Committee has already called for arming the opposition.

Some analysts said Russia's decision to give Syria advanced missiles could set in motion a major international response coordinated by the U.S. and its allies.

"The Russian sale of the S-300 to Syria is a massive game changer," said Anthony Cordesman, of the Center for Strategic & International Studies. "If it is more than a matter of words, and actual transfers take place, it virtually ensures that the U.S.-Russian talks will be meaningless, sends warning signals about similar arms transfer to Iran, can drag Israel into the Syrian fighting, and would sharply alter U.S. and allied 'no fly' capabilities if the Syrians can quickly absorb the system and make it effective."

Secretary of State John Kerry is leading the effort to initiate peace talks between Assad's regime and the anti-government rebels. However, opposition forces say they won't commit to such discussions until Assad steps down -- an increasingly unlikely prospect.

The White House condemned Russia's actions but continued to seek a diplomatic solution amid widespread carnage.

"We've made clear in the past and made clear again," White House press secretary Jay Carney said, "our firm belief that providing arms to the Assad regime does not bring us closer to the political transition that Syria deserves."