President Reagan's consideration of possible economic and political sanctions against Libya appears to be gaining increasing support in Congress. Congressional staff experts on the subject say that should the President decide to act against Libya, he will find considerable sympathy among senators and congressmen. That sympathy already was strong some weeks ago, they say, and now has grown as a result of reports of a Libyan plot against the President's life.
On Dec. 8, Mr. Reagan convened a National Security Council meeting for the second day in a row to consider possible sanctions against Libya in light of reports that Libya had sent ''hit teams'' to assassinate the President and other top American officials. White House Deputy Press Secretary Larry Speakes confirms that Reagan has been getting advice from top national security officials on options for dealing with Libya. The options apparently include a cutoff of oil purchases from that country.
It is unclear how effective such sanctions might be. But for some administration officials and for many in Congress, it is a moral question as much as anything else. Sen. Gary Hart (D) of Colorado is one of those who sees it as at least partly a moral question. In his view, American money spent on oil purchases from Libya help finance Libyan terrorism.
In mid-October, Senator Hart offered an amendment to the foreign assistance authorization that called for a prohibition on American purchases of Libyan oil. That amendment gathered considerable support. A modification offered by Sen. Charles Percy (R) of Illinois calling for study of the question passed the Senate 47 to 44.
But much tougher sanctions than an oil boycott now might be under consideration within the administration. One defense expert who declined to be identified claims that ''there is a group within the administration that wants to overthrow (Libyan leader Colonel Muammar) Qaddafi by force'' by backing other countries that would like to move against Qaddafi.
Ian Butterfield, policy analyst for the conservative Heritage Foundation and a strong advocate of economic action against Mr. Qaddafi, says in a recently published report that the United States cannot shirk such action without being left open to charges that it is hypocritical and unable to match its rhetoric with substantive action. Failure to act, he says, ''would demonstrate to our allies that the US ultimately is unwilling to protect them from Qaddafi's menace.''
But other experts point out that US oil imports from Libya currently are at a low level, amounting only to some 200,000 barrels a day by direct import - less than 4 percent of total US oil imports. Without coordination among its allies who also import oil from Libya, US leverage is limited.
''If the US cut off purchases from Libya, the oil companies could trade Libyan oil in Europe for similar quality oil, which would then be delivered to the United States,' says John Lichtblau, president of the Petroleum Industry Research Foundation, Inc., in New York. ''That's the way things would work unless the US prohibited companies from even lifting the oil.''
West European nations importing oil from Libya are unlikely to boycott Libya. For one thing, as Lichtblau contends, those countries currently have no big arguments with Libya.
Washington, meanwhile, is the scene of debate over whether Qaddafi would be so foolhardy as to try to kill the President of the United States. Reagan's contention that he has ''evidence'' of a Libyan plot against him has gained considerable credibility in Congress. But CBS news on Dec. 7 quoted an unnamed but high-ranking FBI official as saying he had doubts about the evidence.