The United States says it is prepared to offer economic co-operation to North Korea in its latest effort to defuse the crisis over Pyongyang's nuclear programmes.

The US ambassador to South Korea, Thomas Hubbard, said his country could offer more than just food aid to the North - but only if it abandoned its nuclear ambitions.

Russia has meanwhile submitted its own plan to end the crisis, which has seen North Korea reactivate its nuclear facilities.

In South Korea, tens of thousands of people have demonstrated in support of the US military presence there.

'Help with power'

"If [the North Koreans] satisfy our concerns about the nuclear programmes, we are prepared to consider a broad approach," Mr Hubbard said in an interview on South Korea's KBS broadcaster on Sunday.

CRISIS CHRONOLOGY

16 Oct: N Korea acknowledges secret nuclear programme, US says 14 Nov: Oil shipments to N Korea halted 22 Dec: N Korea removes monitoring devices at Yongbyon nuclear plant 31 Dec: UN nuclear inspectors forced to leave North Korea 10 Jan: N Korea pulls out of anti-nuclear treaty 11 Jan: Pyongyang suggests it could resume ballistic missile tests

Timeline of tensions

"That would entail, in the final analysis, some economic co-operation, perhaps in the power field."

Correspondents say Mr Hubbard's comments are the latest sign that Washington is prepared to re-engage with North Korea to defuse the crisis.

Last week, President Bush spoke of a "bold initiative" of benefits for North Korea, signalling that the US might be interested in reopening discussions for the first time since the crisis erupted three months ago.

But the threat of force in retaliation for an attack will always remain, US Defence Secretary Donald Rumsfeld told Fox News on Sunday.

"Does that mean the United States or South Korea would take an attack from North Korea and not respond? Of course not," he said.

Observers say it is possible that North Korea is using the nuclear issue as a ploy to negotiate a non-aggression pact and improved economic aid with the US.

Alternatively, it may have decided that the US intends to attack it anyway and is readying its defences while the US is preoccupied with Iraq.

Opposite view

Mr Hubbard stressed that it was not up to Washington alone to resolve the dispute.

But a statement issued by the official North Korean news agency on Sunday signalled Pyongyang's insistence on direct talks with Washington.

North Korea and the US "should sit face-to-face to solve the nuclear issue on the Korean peninsula," the statement said.

Russia has now given North Korea a plan to defuse the crisis.

"Pyongyang's response will be clear tomorrow [Monday]," Russia's Deputy Foreign Alexander Losyukov said in the North Korean capital.

Reports say the proposals envisage North Korea being given security guarantees and economic help. In return, it would promise to keep the Korean peninsula nuclear-free.

Blood brothers

At least 30,000 South Korean Christians have been demonstrating in the capital, Seoul, supporting the US stance on North Korea and its military presence in the south.

They also prayed for peace.

"Korea and the US are blood brothers," read some placards, while participants waved South Korean and American flags.

The gathering was in contrast to a series of anti-American rallies in the capital in recent weeks.

They began after the acquittal last year of two US servicemen whose armoured vehicle was involved in an accident that crushed two Korean girls to death.