British Foreign Secretary Lord Carrington arrived here tonight on the fourth leg of a journey designed to forge a united front of Western, Mideast and Asian nations against the Soviet takeover of Afghanistan.

The aim of Carrington's talks, along with other international diplomatic efforts, is to supply Pakistan with needed military and economic aid to counter the Soviet expansion toward its border without provoking a greater Soviet response and costing Pakistan its position among nonaligned and Islamic nations.

Carrington will go to New Delhi next to try to persuade India that rearming Pakistan is no threat to them.

The visit of the British foreign secretary here is part of separate but coordinated efforts by the United States and Britain to develop a firm response to the Soviet invasion.

These include U.S. Defense Secretary Harold Brown's just-completed trip to China, a large-scale supplier of arms to Pakistan, and talks in Washington between Agha Shah, foreign affairs adviser to Pakistan President Mohammed Zia ul-Haq, and U.S. Secretary of State Cyrus Vance.

These moves will be followed by a four-day visit here starting Friday of China's Foreign Minister Huang Hua and an emergency meeting of the Islamic foreign ministers' conference here beginning Jan. 26.

Before arriving in Pakistan, which Great Britain more than a century ago used as jumping-off spot to stop Russian expansion into Afghanistan to protect British India, Carrington visited three nations on the area's periphery -- Turkey, Oman and Saudi Arabia.

Both Saudi Arabia and Oman were reported to have expressed great concern over the Soviet takeover and a willingness to spend some of their oil wealth to curtail it.

There have been reports that the Saudis would help finance arms purchases by Pakistan, which would lessen the stigma of such aid being only an American effort and would involve the Islamic world directly in protesting the Soviet takeover of Moslem Afghanistan.

According to sources here, Carrington must tread carefully to avoid making the Pakistanis feel he is a surrogate for the Americans, who in the 1950s were Pakistan's major arms supplier.

This is a new ball game as far as Pakistan is concerned. For the past 21 months officials here have gotten no response to pleas for aid to meet what they saw as the growing menace of Soviet influence in Afghanistan. Now everyone is beating a path to Islamabad.

"There is a great deal of self-satisfaction here," said one well-informed Western diplomat.

Now the Soviets are at the Khyber Pass and Pakistan feels it is the linchpin holding the West together.

"Imagine, God forbid, that there is no Pakistan," said one government official tonight. "The Russians would be pointing like a dagger across the Arabian Sea at the Persian Gulf or curved down to the Indian Ocean and Africa.

"If we can hold the Russians at the Khyber Pass," he continued, "we can protect the Middle East."

All this had emboldened Pakistan, which just a few months ago appeared to be willing to take what it could get from the United States.

Now, said one official, Pakistan would reject token American aid. "Twenty planes and 50 tanks is nothing," he said. "It would annoy India, provoke Russia and be a disservice to Pakistan's national interests."

Instead, according to well-placed sources here, Pakistan would like the United States to start a three-tiered aid program, beginning with the immediate shipment of planes and tanks to go to the Afghan border. After that, Pakistan wants the United States to give it the technical know-how to repair and improve the equipment. In effect, this would make it independent of future American policies that might want to cripple the Pakistan military machine by denying it needed spare parts.

The third phase is economic aid. Where Pakistan a few months ago was talking about the United States rescheduling debt payments for past aid, tonight one official asked, "Why not write it off?"