Manchester United are this week expected to increase their offer for Dimitar Berbatov but will still fall short of the £30m that Tottenham Hotspur regard as a minimum for the 27-year-old striker.

But United have also told Spurs that they must drop their complaint to the Premier League alleging that they had inappropriately pursued the Bulgaria international. The demand has caused anger at Spurs who had hoped that United would apologise to facilitate the deal – as Liverpool were forced to when signing Robbie Keane earlier in the summer.

However, given the breakdown in relations between Spurs and Berbatov after he put in a transfer request and then claimed he wasn't "psychologically ready" to play for the club, it appears that a deal could finally be struck for between £25m and £28m. Spurs are considering making a €15m (£12m) bid for the prolific Colombian striker Falcao as they desperately attempt to improve their attacking options.

Relations between United and Spurs remain fraught but equally strained are relations between Berbatov and Spurs. He was left out of the squad for Saturday's 2-1 home defeat to Sunderland, despite scoring two goals for Bulgaria in midweek, with head coach Juande Ramos calling it a "strange and conflicting situation". The club also accused the striker of being a disruptive presence in the dressing room. Ramos said Berbatov's behaviour had "repercussions" for the rest of the team.

Nevertheless, Berbatov did train on Saturday with other players who were omitted from the squad to play Sunderland and he also held talks yesterday with Ramos. The head coach wanted to ascertain directly from Berbatov, and his agent Emil Dantchev, who flew in for the meeting, how determined he was to leave Spurs before the transfer window closes. The Spurs board have not yet fined Berbatov for his behaviour but are considering whether to do so.

Spurs have also been bitterly disappointed that despite their attempts to raise interest in Berbatov from other clubs, primarily in Spain, United – who tried to buy him last summer – are still the only serious bidders. Their initial offer of £20.5m was rejected, with Spurs insisting they wouldn't accept less than £32m, although it now appears they may have to do so.

Having sold Keane to Liverpool for £19m Spurs are desperately short of strikers and have been frustrated in their attempts to sign replacements. Bids for the Russian pair of Andrei Arshavin and Roman Pavlyuchenko have failed with the former's club Zenit St Petersburg asking for more money, and Spurs claiming to have moved on to other targets, while the latter has indicated he doesn't want to move to White Hart Lane. Spurs have also not progressed in their efforts to sign Roque Santa Cruz and Diego Milito while they have denied being interested in Dean Ashton, Diego Forlan and Freddie Kanouté.

But Spurs' representatives were in Argentina at the weekend to watch the 22-year-old striker Falcao – full-name Radamel Falcao Garcia Zarate – score for River Plate in their defeat to Banfield. Spurs accept that they need to buy at least two strikers if Berbatov is sold after a disastrous start to the season.

United, who play Portsmouth tonight, do not have another league game until they face Liverpool away on 13 September as they play in the European Super Cup this Friday against Zenit, which may further strengthen their bargaining power with Spurs. They are also looking to off-load Louis Saha who has previously been a Spurs target.

The situation is causing frustration at White Hart Lane even though they would be more than doubling the £10.9m they paid for Berbatov two years ago.

Speaking after the defeat to Sunderland Ramos admitted that he had never had a similar situation with a player. "Players go through physical fitness issues, good or bad and in this case it's psychological and we've just go to deal with it," he said.

When told that the Sunderland manager, Roy Keane, had said he would drive away any player who said he didn't want to play for his club, Ramos replied: "Roy Keane is a great manager and has been a great footballer, with a lot of experience, so that's an interesting point of view. Yes, a very interesting point of view."