* FTSE 100 up 0.3%, FTSE 250 down 0.2%
* U.S. tariffs on China to remain in place for now
* Tullow Oil drags midcaps lower
* Banks drop on rate cut bets (Adds company news items, updates to closing prices)
Jan 15 (Reuters) - London's main share index rose slightly on Wednesday, hours before the sealing of an initial U.S.-China trade deal, though sentiment was tempered when Washington said tariffs on Chinese goods would not be rolled back immediately.
The FTSE 100 rose 0.3% on a third day of gains, supported by a host of so-called defensive stocks including pharmaceutical giants AstraZeneca and GlaxoSmithKline , which rose nearly 2%, and consumer goods companies.
Investors tend to turn to these sectors at times of macroeconomic uncertainty.
The FTSE 250 ended 0.2% lower, with a 16% plunge in Tullow Oil weighing the most. Tullow said it would take a $1.5 billion writedown after cutting its long-term oil price assumptions.
Investors betting on a quick de-escalation of Sino-American tensions were dealt a blow when U.S. Treasury Secretary Steven Mnuchin said tariffs on Chinese goods would not be repealed until the completion of a Phase 2 agreement.
"Strategic competition between the U.S. and China, especially in tech, is likely to persist despite a limited 'Phase 1' trade deal," BlackRock analysts wrote in their weekly note.
"The U.S.-China trade conflict 2019's dominant geopolitical risk has paused, yet we expect enduring strategic rivalry between the two countries."
Banks suffered across the board as weak inflation data further spurred hopes that the Bank of England will cut interest rates in its January meeting. Low interest rates squeeze a lender's margins.
Royal Bank of Scotland, which also had its rating downgraded by Barclays, led the sub-index down 1% to a one-month low with a 2.5% share price fall.
Keeping a lid on losses on the midcap bourse, Provident Financial jumped 7% after its key credit card business enjoyed a better-than-expected fourth quarter and Hochschild Mining climbed 3% on better-than-expected 2019 production.
Among smaller stocks, fast fashion retailer QUIZ tanked nearly 20% on its worst day since June, as it pointed to poor trading over the key Christmas period. (Reporting by Shashwat Awasthi and Muvija M in Bengaluru, Editing by Sherry Jacob-Phillips and Shailesh Kuber)