President Reagan, despite considerable pressure from conservative Republicans to change U.S. policy toward socialist Mozambique, yesterday reassured President Joaquim Chissano of continuing American support and offered to help "in any way that we can" to end the guerrilla war there.

Following a half-hour White House meeting, a senior administration official said Reagan had discussed with Chissano his government's struggle against South African-backed rebels and that both agreed it had to be brought to an end.

"The president made it clear on our side that we are prepared to be helpful, as we have in the past, in that regard in any way that we can," the official said. "President Chissano said he would want to be in continuing contact with us about that."

Later, in an interview with Washington Post editors and reporters, Chissano said he had asked Reagan for increased U.S. economic aid and told him "about our readiness to receive military aid of any kind."

Chissano said he had stressed that nonlethal aid would be useful

if the administration was un- able to provide other military assistance because of "difficulties in that field."

He was apparently referring to strong pressure on the White House from conservative Republicans, led by Sen. Jesse Helms (R-N.C.) and Minority Leader Robert J. Dole (R-Kan.), to end U.S. aid to the central Mozambican government and provide support for the self-described anticommunist opposition movement.

The United States this year is providing Mozambique with $10 million in economic aid, mainly for the private sector, and $75 million in food assistance. A past administration effort to gain congressional approval of nonlethal military aid was blocked by conservatives.

The administration has been trying to wean Mozambique, whose Marxist ruling party has a close relationship with Moscow, from its East Bloc ties.

Even as Reagan and Chissano were meeting, the Mozambican National Resistance (Renamo) held a news conference on Capitol Hill in which Grover Norquist, an aide to Republican presidential candidate Pierre S. (Pete) du Pont IV, said he had briefed Reagan on Sept. 22 about Renamo's political and economic program.

Norquist asserted that after his briefing, which included a sharply critical report on Chissano and his government, Reagan had said, "You have certainly changed my agenda for when I meet Chissano."

But there was no indication from accounts of yesterday's White House meeting that the president had changed his mind. The senior U.S. official, briefing reporters afterwards, said the meeting had "consolidated" what he called a "constructive relationship" between the administration and the Chissano government.

It was Reagan's first meeting with Chissano, who became Mozambique's leader after the death of President Samora Machel in an airplane crash inside South Africa last October.

Chissano said Reagan "very emphatically" assured him of continued U.S. support but had warned there would be "some difficulties" in adding any more aid because of severe budget cuts.

Chissano said Reagan never referred to Renamo by name, but talked about "the division" inside Mozambique and whether the two sides "could not sit down and speak . . . in order to find a solution."

"We explained to him what we thought about this so-called division, a fake division. There is no division. Renamo does not represent the interests of anyone among the people of Mozambique but the interests of South Africa," Chissano said.

He said he had seen no evidence of secret U.S. aid to Renamo other than private support from conservative groups but asserted that South Africa was still providing supplies to the rebels by clandestine airdrops.

The Mozambican leader said he thought the government could win the war against Renamo "militarily" but that this would result in heavy loss of lives. He said his government was using "other methods of persuasion" and "political means" to try to end the fighting.