President Reagan in his news conference Tuesday night gamely sought to dispel the growing public unease over his policies in Central America. His language seemed fairly measured and temperate. He declared that ''there's not going to be anything like Vietnam'' in Central America and the United States ''is not seeking a larger presence in that region.'' He also stressed his commitment to a peaceful regional solution and to economic aid as the weightiest aspect of US diplomacy. The President should be given credit for trying to calm public fears and for a more conciliatory posture.
Whether Mr. Reagan managed to end the public uncertainty about the administration's present course is doubtful, however. Nagging questions still need to be addressed if he is to build bipartisan support and bring the country along with him as he deals with a complex and difficult situation:
* What is the true aim of the US military maneuvers off the coasts of Nicaragua and in Honduras? The President describes them as routine. If this is so, they would have been better planned. They also would not be more extensive than is normal. Is the US simply flexing its military muscle as a prelude to serious negotiation? Is it only warning Cuba? Or is it, as some critics fear, part of an effort to bring down the Sandinista government? Americans cannot be blamed for their concern about this show of military force, coming as it does just when the Contadora countries - Mexico, Panama, Venezuela, and Colombia - are seeking to mediate a regional settlement and when the Nicaraguan government has put out its own peace feelers.
* What is the purpose of US covert aid in Nicaragua? Is it to interdict the supply of arms into El Salvador as the President claims? Or to overthrow the Sandinistas? Suspicion is strong that the latter is the case: One, because no strong proof of such arms shipments has been presented. Two, because the ''contras'' fighting in Nicaragua with US aid clearly are attacking the Sandinista regime. If the contras do not succeed - and it does not appear that US help is working - there is risk of a civil war which, the President's assurances notwithstanding, could drag the US into a Vietnam-like morass.
* Is the US making a good faith effort to talk with Nicaragua? The President does not like the leftist direction in which the Sandinistas are moving. Few do. But that is all the more reason to keep talking - not with a view to demanding the kind of democracy which never did exist in Nicaragua but to reaching an agreement on the export of revolution to neighboring countries. The US after all helped put the Sandinistas in power by getting rid of Somoza. That the Sandinista regime is now turning into another dictatorship is not altogether surprising, but why should that inhibit a continuing dialogue?
In this connection Mr. Reagan said he was ''heartened'' by the efforts of the Contadora group. By working more closely with these nations, and letting them carry the ball, the US would not only lower its own profile to advantage but put the responsiblity on those who have the most immediate stake in stability in the region. If the Contadora group is effective, splendid. If not, then the United States would have to try something else.
In sum, the President may have succeeded in calming war jitters. He also touched on the fundamental solution of the Central America problem: economic development. But, having left the latter issue to a bipartisan commission which will not report until next year, and having conspicuously chosen to apply more military pressure in the short term, he will have to respond to lingering concern about where the US is really headed.