Strength in risk-sensitive miners helped lift Britain's top shares on Tuesday, with investors encouraged by signs of progress towards a political compromise on the US “fiscal cliff”.

Investors were more hopeful of a deal to head off spending cuts and tax rises that could drive the United States back into recession after a source said President Barack Obama had offered a new compromise, including on tax hikes for the wealthy.

At 13:58 SA time, the FTSE 100 was up 21.20 points, or 0.4 percent, at 5,933.35, recovering after falls of 0.2 percent on Monday and resuming a rally which last week took the index to within 20 points of its 2012 closing peak at 5,965.

“If we do get final confirmation (on the fiscal cliff) then the FTSE does have a chance of heading towards the year highs and testing them,” Angus Campbell, head of market analysis at Capital Spreads said.

“We may potentially end the year off with a six in front of the FTSE 100, but it depends... because if the deal's done with only a day to go... then it may not give the index enough time.”

Gains by heavyweight miners provided over 7 points of the FTSE 100's advance, buoyed by hopes the demand picture for metals will recover once the US budget issues are resolved.

Recent upbeat data from top metals consumer China also benefited a sector which has fallen over 1.5 percent in 2012, a big underperformance compared with the FTSE's 6.3 percent rise.

Away from the miners, G4S was a top blue chip gainer, up 2.6 percent with traders citing the impact of a broker upgrade as well as a Financial Times report saying the security firm is set to win a role in implementing the government's contentious and complex changes to child benefit and the universal credit.

Panmure Gordon raised its rating for G4S to “buy” from “hold” with an increased target price of 295 pence, up from 262 pence, which is broadly in line with the peak seen before the sharp falls by the stock after the Olympic Games contract debacle which dogged the company earlier this year.

Temporary power firm Aggreko also bounced back, adding 2.6 percent after posting a 22 percent drop on Monday when the firm issued its second profit warning in two months, with Seymour Pierce reiterating its “buy” rating on the stock.

“(Aggreko) has a phenomenal track record and yesterday's profit warning should not be seen as evidence that the business model is broken. Long term growth prospects remain solid. ... Investors should look beyond this short term volatility and take advantage of the price reduction,” Seymour Pierce said in a note.

Trading volume in Aggreko was the biggest among the blue chips at over twice its 90-day daily average by mid-session, with overall FTSE 100 volume at less than a third of its 90-day daily average.

As investors became increasingly confident that a US budget deal could be reached, defensively perceived sectors such as drinks groups and drugmakers, which tend to do well even in harsh economic times, fell back.

Fresh falls by market heavyweight Vodafone, down 1 percent, was the main drag on the blue chips, with the stock extending Monday's 1.7 percent decline and knocking over 3 points off the index on concerns about higher costs for mobile operators after the Dutch state raised much more than expected in its auction of fourth generation (4G) frequencies. - Reuters