The United States is willing to provide "significant" assistance, including the supplying of tear gas and other nonlethal military equipment, to help the new government in El Salvador combat extremist violence, a senior U.S. official said yesterday.

The official, who asked not to be identified, stressed that the El Salvador government, which took power in a military coup earlier this month, has not yet asked the United States for either military or financial assistance.

However, he and other U.S. officials said there is a broad consensus in the Carter administration that the new government, which displaced rightist President Carlos Humberto Romero, is sincerely trying to ease the repression and heal the ideological divisions between left and right that have caused escalating violence in that tiny Central American country.

But the conciliatory gesturs made by the moderate military officers heading the new government have met with resistance from leftist groups that has erupted into new bloodshed. Still, the U.S. sources said, the feeling here is that the government offers the best hope of averting a takeover of El Salvador by extreme leftists and is deserving of U.S. help.

The sources said, however, both the Salvadoran leaders and U.S. policymakers agree that a big influx of U.S. aid at this time would have the harmful effect of making the new government appear to have what one source called a "made-in-the-U.S.A." label.

For that reason, the sources said, the decision has been made to move cautiously and wait until the Salvadoran leaders signal their desire for U.S. aid.

In the meantime, the sources added, the administration is making a modest beginning by tacking a request for $5 million in economic assistance for El Salvador and Honduras to a planned supplemental request for funds to help Nicaragua recover from the ravages of civil war.

The proposed aid package, which is still under debate within the administration, stems in part from President Carter's Oct. 1 pledge to combat Soviet and Cuban influence in the Caribbean area through greater efforts to "alleviate the unmet economic and human needs" of the region.

According to the sources, when the supplemental requests are forwarded to Congress, they probably will include, in addition to the $5 million for El Salvador and Honduras, $75 million for Nicaragua and $25 million for the islands of the Eastern Caribbean.

In addition, the sources said, the administration is studying ways in which aid funds already approved by Congress could be diverted to El Salvador and other Caribbean-area countries if the need arises.